National Climate Report - May 2018
Maps and Graphics
U.S. Percentage Areas
Supplemental May 2018 Information
- 2018 High Tide Flooding Report
- Year-to-date temperature evolution for select U.S. cities
- Year-to-date precipitation evolution for select U.S. cities
- May and spring county temperature and precipitation maps
- Regional warmest/wettest summer
- Climate Highlights — May
May Average Temperature Departures
May Percent of Average Precipitation
- For May, the average contiguous U.S. temperature was record warm at 65.4°F, 5.2°F above the 20th century average. This surpassed the previous May record of 64.7°F set in 1934.
- Above-average May temperatures stretched from coast to coast with every state having an above-average temperature. Record warmth was observed in parts of the Northwest and stretching from the Southern Plains through the Midwest and into the Mid-Atlantic. Forty-two states had monthly temperatures that were much above average with eight of those states – Arkansas, Illinois, Indiana, Kentucky, Missouri, Ohio, Oklahoma and Virginia – being record warm.
- The contiguous U.S. average maximum (daytime) temperature during May was 78.3°F, 5.4°F above the 20th century average, marking the second warmest value on record. Only May 1934 had a warmer maximum temperature at 79.3°F. Above-average maximum temperatures spanned the nation with four states from Oklahoma to Indiana being record warm. Parts of the West had near-average maximum temperatures with below-average maximum temperatures for Florida where the record precipitation helped to suppress daytime temperatures.
- The nationally averaged minimum temperature (overnight lows) was exceptionally warm during May at 52.5°F, 5.1°F above average and 2.0°F warmer than the previous record set in 1987. Fourteen states had a May minimum temperature that was record warm with 29 additional states having much-above-average minimum temperatures. Only Maine had a near-average minimum temperature during May.
- During May there were 8,596 record warm daily high (3,789) and low (4,807) temperature records, which was more than 18 times the 457 record cold daily high (313) and low (144) temperature records. Several of the daily records were noteworthy, including 100°F on May 28 in Minneapolis, Minnesota – the earliest such occurrence on record.
- Based on NOAA's Residential Energy Demand Temperature Index (REDTI), the contiguous U.S. temperature-related energy demand during May was 24 percent above average and ranked near the middle value in the 124-year period of record.
- The May precipitation total for the contiguous U.S. was 2.97 inches, 0.06 inch above average, and ranked near the middle of the 124-year period of record.
- Record and near-record precipitation was observed across the Southeast and Mid-Atlantic, partially due to two slow-moving weather systems, including Subtropical Storm Alberto in late May. Flooding and mudslides were widespread across the region, and Florida and Maryland each had their wettest May on record. On the station level, Asheville, North Carolina, the home of NCEI headquarters, observed its wettest month of any month on record, with 14.68 inches of rain. Several other locations, including Key West, Florida, had their wettest May on record. Above-average precipitation was also observed across parts of the West, Central Plains and Midwest.
- Below-average precipitation was observed along the West Coast, Southwest, Southern Plains, the Northeast and parts of the Midwest. The combination of warm and dry conditions contributed to ongoing drought concerns across these regions.
- After observing record-high spring snowpack across the interior Northwest and Northern Rockies, above-average May temperatures and precipitation caused rapid snowmelt, flooding rivers across the region. Flooding was observed in parts of Idaho, Montana, Washington and Wyoming.
- Alaska had its fourth wettest May on record with 2.98 inches of precipitation, 0.87 inch above average. This was the wettest May for the state since 1998. Interior and southern parts of Alaska were particularly wet, with below-average precipitation for some northern and northwestern parts of the state. Eagle, Alaska had its wettest May on record with almost 250% or normal precipitation while Bettles had its second wettest May on record.
- According to the May 29 U.S. Drought Monitor report, 26.4 percent of the contiguous U.S. was in drought, down from 28.6 percent at the beginning of May. Drought conditions improved in the Southeast and parts of the Plains. Drought conditions intensified and expanded in parts of the Southwest, interior Northwest, Southern Plains and Northern Plains. Abnormally dry conditions developed across leeward locations on the Hawaiian Islands.
- Climate Highlights — spring (Mar-May)
Mar-May Average Temperature Departures
Mar-May Percent of Average Precipitation
- During meteorological spring (March-May), the warm May more than balanced the cold April. The seasonally averaged temperature for the Lower 48 was 52.4°F, 1.5°F above average and ranked as the 22nd warmest spring on record.
- Above-average temperatures were observed across parts of New England and from the West Coast to the Southern Plains. Four states in the Southwest and Southern Plains had one of their 10 warmest springs on record.
- Across much of the East, the warm May counterbalanced the cold April, resulting in a near-average spring temperature. In the Great Plains and Midwest, the temperature jump from April to May was stark. For example, Wisconsin had its coldest April on record, followed by its second warmest May, with a month-to-month temperature increase of 28.6°F.
- The contiguous U.S. average maximum (daytime) temperature during March-May was 64.7°F, 1.6°F above the 20th century average, marking the 24th warmest value on record. Above-average maximum temperatures were observed across the West with much-above-average temperatures in parts of the Southwest and Southern Plains. Near- to below-average maximum temperatures were observed through the Northern Plains, Midwest, and across much of the East.
- The contiguous U.S. March-May minimum (nighttime) temperature was 40.1°F, 1.4°F above average, and ranked as the 23rd warmest on record. Above-average minimum temperatures were observed across the West and scattered parts of the Midwest and East Coast. Near- to below-average minimum temperatures were observed across parts the Northern Plains, Great Lakes and Southeast.
- Based on NOAA's Residential Energy Demand Temperature Index (REDTI), the contiguous U.S. temperature-related energy demand during March-May was 21 percent above average and ranked near the middle value in the 124-year period of record.
- The spring precipitation total was 7.91 inches, 0.03 inch below average, and ranked near the middle value of the 124-year period of record.
- Above-average spring precipitation was observed across parts of the West and along parts of the East Coast. Below-average precipitation was observed for most of the central U.S., Southwest, and parts of the Northeast. Arizona and New Mexico each had their 10th driest spring on record. The warm and dry spring, particularly across parts of the Great Plains, could impact the upcoming growing season in agricultural regions.
- The U.S. Climate Extremes Index (USCEI) for spring was five percent below average and ranked near the median value in the 109-year period of record. Despite the below-average national value, there were elevated extremes in warm maximum and minimum temperatures and one-day precipitation totals. The component that examines one-day precipitation totals was the fifth highest on record for the season. This was the lowest March-May CEI since 2014. The USCEI is an index that tracks extremes (falling in the upper or lower 10 percent of the record) in temperature, precipitation and drought across the contiguous United States.
- On the regional scale, the CEI was the second highest on record for the Southwest due to extremes in warm maximum and minimum temperatures, the spatial extent of dry conditions, one-day precipitation totals and days without precipitation.
- Climate Highlights — year-to-date (January-May)
Jan-May Average Temperature Departures
Jan-May Percent of Average Precipitation
- During the first five months of 2018, contiguous U.S. average temperature was 45.0°F, 1.6°F above the 20th century average and was the 21st warmest January-May on record.
- The year-to-date has been marked by large swings in temperatures, particularly from the Great Plains to East Coast. When averaged for the first five months of the year, much of the West, Southern Plains and East Coast were warmer than average. Nine states had a year-to-date temperature that was much above average. Near- to below-average temperatures were observed across the Northern and Central Plains and Midwest.
- The Alaska year-to-date temperature was 20.7°F, 4.9°F above average, ranking as the ninth warmest on record. Much-above-average temperatures were observed across western and northern Alaska with record warmth along parts of the Aleutians. The record low sea ice for parts of the year in the Bering and Chukchi seas likely contributed to the Alaskan warmth. Southern parts of Alaska had a near-average year-to-date temperature.
- The contiguous U.S. average maximum (daytime) temperature during January-May was 56.8°F, 1.8°F above the 20th century average, marking the 18th warmest value on record. Above-average maximum temperatures were observed across the West with much-above-average temperatures in parts of the Southwest. Above-average conditions were also observed for parts of the Mid-Atlantic and Northeast. Near- to below-average maximum temperatures were observed through the Northern Plains and Upper Midwest.
- The contiguous U.S. January-May minimum (nighttime) temperature was 33.1°F, 1.4°F above average, and ranked as the 25th warmest on record. Above-average minimum temperatures were observed across the West, Southern Plains and much of the East. Near- and below-average minimum temperatures were observed in the Northern and Central Plains and parts of the Upper Midwest.
- Based on REDTI, the contiguous U.S. temperature-related energy demand during January-May was 12 percent below average and ranked near the middle value in the 124-year period of record.
- The year-to-date precipitation total was 12.66 inches, 0.27 inch above average, and ranked near the middle value of the 124-year period of record.
- Much of the eastern U.S. was wetter than average for the first five months of the year, with much-above-average precipitation across parts of the Midwest, Mid-Atlantic and Northeast. Pennsylvania, New Jersey, Rhode Island and West Virginia each had a top ten wet January-May. Above-average precipitation was also observed across parts of the Northern Rockies and Plains, which fell mostly as snow earlier in 2018. Below-average precipitation was observed across much of the Southwest, Great Plains and Upper Midwest.
- The USCEI for the year-to-date was five percent above average and ranked near the median value in the 109-year period of record. Despite the below-average national value, there were elevated extremes in warm maximum and minimum temperatures and one-day precipitation totals. The component that examines one-day precipitation totals was the highest on record. This was the lowest January-May CEI since 2013.
- On the regional scale, the CEI was record high for the Southwest due to extremes in warm maximum and minimum temperatures, the spatial extent of dry conditions and one-day precipitation totals.
These regional summaries were provided by the six Regional Climate Centers and reflect conditions in their respective regions. These six regions differ spatially from the nine climatic regions of the National Centers for Environmental Information.
- Northeast Region: (Information provided by the Northeast Regional Climate Center)
- The average temperature for the month of May in the Northeast was 61.2 degrees F (16.2 degrees C), which was 4.9 degrees F (2.7 degrees C) above normal, ranking this as the fifth warmest May on record for the region. All twelve states in the Northeast ranked this May amongst their 20 warmest on record: Rhode Island and West Virginia, second warmest; Pennsylvania, Maryland, and Massachusetts, third warmest; Connecticut and Delaware, fourth warmest; New Jersey, fifth warmest; New York, seventh warmest; New Hampshire, tenth warmest; Vermont, 11th warmest; and Maine, 19th warmest. May temperature departures ranged from 2.1 degrees F (1.2 degrees C) above normal in Maine to 7.5 degrees F (4.2 degrees C) above normal in West Virginia. Below normal temperatures in March and April throughout much of the region combined with the warmth from May lead to an average spring temperature of 45.1 degrees F (7.3 degrees C) in the Northeast, which was 0.5 degrees F (0.3 degrees C) below normal. Spring wrapped up on the cooler side of normal for eight states in the region, with three states above normal and New Hampshire at normal. Spring temperature departures for the Northeast ranged from 1.1 degrees F (0.6 degrees C) below normal in New York to 0.4 degrees F (0.2 degrees C) above normal in Maine.
- The Northeast received 3.91 inches (99.3 mm) of precipitation, which was 97 percent of normal. Seven states were drier than normal and five were wetter than normal. Maryland received 7.68 inches (195.1 mm) of precipitation, or 186 percent of normal, and experienced its wettest May on record. Delaware received 7.18 inches (182.4 mm) of precipitation, ranking this May as their fourth wettest on record. New Jersey received 5.96 inches (144.5 mm) of its normal precipitation, making this month their 13th wettest on record. Receiving 6.03 inches (153.2 mm) of precipitation, West Virginia ranked this May as their 15th wettest on record. New Hampshire received only 1.63 inches (41.4 mm), or 40 percent, of its normal precipitation, causing this month to be their 11th driest May on record. This May was the 17th driest on record for Maine and Vermont and the 20th driest for Massachusetts. The Northeast received 11.53 inches (292.9 mm) of precipitation during spring, which was 103 percent of normal. West Virginia, Delaware, Maryland, and New Jersey all ranked this spring as their 15th wettest on record. Precipitation across the twelve states ranged from 78 percent of normal in New Hampshire to 124 percent of normal in Delaware.
- At the beginning of May, 40 percent of Maryland was abnormally dry, and it was the only state in the region that was experiencing abnormal dryness. Throughout the month, these dry conditions improved as a result of the abundant rain that impacted much of the southern states within the region. The US Drought Monitor released May 29 showed New Hampshire as the only state to have dry conditions, with 18 percent of the southern part of the state experiencing abnormal dryness. Drought conditions improved in the Northeast during spring, with two percent of the Northeast being abnormally dry at the beginning of March and less than one percent of the region experiencing abnormal dryness by the end of May.
- Torrential rain over Memorial Day weekend brought catastrophic flooding to parts of Maryland as the Patapsco River quickly rose and inundated local communities, prompting the National Weather Service to issue a flash flood emergency, its most severe flood alert. At the beginning of the month, a large line of severe thunderstorms moved through much of the Northeast on May 4. Wind gusts up to 74 miles per hour (33.1m/s) were reported in Wells, Vermont with tree damage spreading throughout much of the central part of the state. Hail was reported in Syracuse, New York and numerous trees were down in Utica, New York. Rivers were overflowing their banks and flooding streets near the Interstate 64 corridor in West Virginia as a result of heavy rain on May 5 and 6. A severe weather outbreak on May 15 brought intense downpours which caused flooding, trapped people in cars, and led to road closures. Large hail was reported in several states. There were strong winds that downed trees and power lines that caused over 600,000 customers in Pennsylvania, New York, New Jersey, and Connecticut to lose power. There were seven confirmed weak tornadoes (EF-0 or EF-1) and one EF-2 tornado in Putnam County, New York. Several downbursts in New York and Connecticut were reported from these storms, as well as unfortunately five deaths. Train line services were suspended, stranding thousands during rush hour. A state of emergency was declared for parts of New York. Pottstown, Pennsylvania reported a gust of 81 miles per hour (36.2 m/s). On that same day, tennis ball-size hail was reported in Columbia County, New York, with additional reports of shattered windshields from hail across Pennsylvania and Connecticut. Multiple downbursts with wind speeds up to 110 miles per hour (49.2 m/s) were also reported in Wayne County, Pennsylvania. Macrobursts near Fairfield, Connecticut and across Dutchess County, New York were observed, downing trees and power lines. Many schools in Connecticut were closed for more than two days after these storms from residual damage and power outages. The changes in atmospheric pressure from these storms were so powerful that a meteotsunami formed on Long Island Sound, as noted by a tidal gauge in New Haven, Connecticut which showed water levels fluctuating up to a foot more than normal for several hours. Between May 21 and 22, three sinkholes appeared in Frederick and Annapolis, Maryland, and closed part of Route 450 as a result of heavy rain and flash flooding. Severe flooding killed one person trying to rescue another person as the Patapsco River in Maryland began to overflow its banks on May 27. Unrelenting rain led to serious flooding in Ellicott City, Maryland where estimates show the Patapsco River rose 17.8 feet (5.4 m) in less than two hours. In total, over nine inches (228.6 mm) of rain were reported near Catonsville, Maryland from this flooding event. Less than two years ago, this same city experienced a similar flooding situation when 6.5 inches (165 mm) of rain fell within three hours in July of 2016. As Ellicott City was just finishing rebuilding from the 2016 flood event, the flood from this year heavily damaged buildings and houses along the city's Main Street, and caused more than $20 million in damage.
- For more information, please go to the Northeast Regional Climate Center Home Page.
- Midwest Region: (Information provided by the Midwest Regional Climate Center)
- May temperatures in the Midwest set a new record (1895-2018 period of record) averaging 66.3 degrees F (19.1 C) which was 6.9 degrees F (3.8 C) above normal. Five Midwest states (Illinois, Indiana, Kentucky, Missouri, and Ohio) set statewide records for May while the remaining four states ranked among the five warmest Mays in their respective histories. Temperatures reached the triple-digit readings (100 degrees F or 38 C) in multiple stations in Illinois, Iowa, Minnesota, and Missouri. Spring temperatures averaged to near normal across the region with the very cold April (2nd coldest) and the record warm May largely offsetting each other. Temperatures were within 2 degrees F (1 C) of normal for nearly all of the Midwest. Some small areas in the north were slightly more than 2 degrees F (1 C) below normal.
- May precipitation varied across the Midwest with the majority of the region below normal. Totals ranged from less than 50 percent of normal in parts of Illinois, Indiana, and Minnesota to more than twice normal in southern Wisconsin and southwestern Michigan. Spring precipitation totals were above normal in the easternmost states, along the southern extent of the region, and from the Iowa-Minnesota border eastward across southern Wisconsin into lower Michigan. Drier than normal swaths stretched across the northern extent of the region and through central areas including the southern two-thirds of Iowa, northwestern two-thirds of Missouri, much of Illinois, and nearly all of Indiana.
- Spring planting of corn and soybeans caught up to the 5-year average in most of the region in May. Cool and wet weather in April put most of the Midwest 1 to 3 weeks behind but as warmer and drier condition allowed farmers into the field they quickly made up for lost time. Soybeans were caught up across the Midwest and corn was as well except in Michigan where it remained about a week behind the 5-year average.
- Drought areas in the Midwest were less than 5 percent of the region throughout May. The area in northern Minnesota that started the month in moderate drought saw conditions improve and drought end. In northern Missouri and southern Indiana, a larger area of moderate drought also had an area of severe drought develop in northwest Missouri where spring rainfall was less than half of normal.
- Early May saw what was likely the last freeze of the season for most stations in the northern third of the region, as well as some stations in the eastern third. Some of the southern Ohio and Kentucky stations that had a May freeze were later than normal, but the northern locations were typically a little earlier than normal.
- For further details on the weather and climate events in the Midwest, see the weekly and monthly reports at the Midwest Climate Watch page.
- Southeast Region: (Information provided by the Southeast Regional Climate Center)
- Temperatures were well above average across much of the Southeast region during May, but near average to slightly below average across the Florida Peninsula, Puerto Rico, and the U.S. Virgin Islands. Monthly mean temperatures ranged from 3 to as much as 8 degrees F (1.7 to as much as 4.4 degrees C) above average for nearly 65 percent of the 209 long-term (i.e., period of record equaling or exceeding 50 years) stations across the region. Half (104 of 209) of the long-term stations observed monthly mean temperatures that were ranked within their five warmest values on record, and over 60 percent of these stations were located in North Carolina and Virginia. Virginia observed its warmest May since records began in 1895. Twenty-six stations across the region observed or tied their highest May mean temperature on record, including Muscle Shoals, AL (1893-2018; 76.0 degrees F, 24.4 degrees C), Atlanta, GA (1879-2018; 74.8 degrees F, 23.8 degrees C), Raleigh, NC (1887-2018; 74.2 degrees F, 23.4 degrees C), Richmond, VA (1897-2018; 73.4 degrees F, 23.0 degrees C), Greensboro, NC (1903-2018; 73.2 degrees F, 22.9 degrees C), and Roanoke, VA (1913-2018; 72.5 degrees F, 22.5 degrees C). Average daily minimum temperatures were exceptionally warm across the northern half of the region, as the persistent influx of tropical moisture suppressed nighttime cooling during the month. Numerous long-term stations observed or tied their highest count of days during May with a minimum temperature at or above 70 degrees F (21.1 degrees C), including Gainesville, FL (1891-2018; 15 days), Columbia, SC (1888-2018; 15 days), Columbus, GA (1902-2018; 12 days), Fayetteville, NC (1910-2018; 11 days), and Norfolk, VA (1874-2018; 11 days). The warmest weather of the month across the Southeast occurred from the 11th through the 13th, as a westward expansion of the Bermuda High over the region produced unseasonably warm temperatures. Daily maximum temperatures reached at least 90 degrees F (32.2 degrees C) across much of the region, with portions of nearly every state exceeding 95 degrees F (35 degrees C). On the 13th, Pensacola, FL (1880-2018) tied its second highest daily maximum temperature on record for May, reaching 98 degrees F (36.7 degrees C). In contrast, the coolest weather of the month occurred on the 1st, as a continental high pressure system ushered in cool, dry air from Canada. Daily minimum temperatures fell below 55 degrees F (12.8 degrees C) as far south as northern Florida, while numerous stations in North Carolina and Virginia recorded minimum temperatures ranging from 25 to 35 degrees F (-3.9 to 1.7 degrees C).
- Precipitation was well above normal across much of the Southeast region during May. Monthly precipitation totals ranged from 200 to more than 500 percent of normal in broad portions of every state. Eighty-eight of the 209 long-term stations across the region observed May precipitation totals that were ranked within their five highest values on record, and nearly 60 percent of these stations were located in Florida and North Carolina. Florida observed its wettest May since records began in 1895. Twenty-three stations across the region observed their wettest May on record, including Stuart, FL (1936-2018; 24.20 inches, 615 mm), Lakeland, FL (1949-2018; 19.19 inches, 487 mm), Asheville, NC (1869-2018; 14.68 inches, 373 mm), Wilmington, NC (1871-2018; 14.36 inches, 365 mm), Charleston, SC (1938-2018; 10.62 inches, 270 mm), and Richmond, VA (1887-2018; 10.35 inches, 263 mm). This was also the wettest month all time for Stuart, FL and Asheville, NC, which surpassed their previous records in June 1999 (19.98 inches, 507 mm) and August 1940 (13.75 inches, 349 mm), respectively. Jocassee 8 WNW (1950-2018) observed the highest May precipitation total on record for the state of South Carolina, with 17.96 inches (456 mm). Port Salerno 5 W (2003-2018; 24.47 inches, 622 mm), Lake Toxaway 2 SW (1952-2018; 23.50 inches, 597 mm), and Helen (1956-2018; 19.14 inches, 486 mm) observed the second highest May precipitation total on record for the states of Florida, North Carolina, and Georgia, respectively. Several long-term stations in Florida and Georgia observed their highest count of days during May with measurable precipitation, including Key West, FL (1871-2018; 21 days), Sanford, FL (1949-2018; 18 days), Athens, GA (1857-2018; 17 days), and Sarasota-Bradenton, FL (1911-2018; 16 days). From the 13th through the 19th, Washington, D.C. (1871-2018) and Washington Dulles International Airport, VA (1962-2018) observed their longest streak of 7 consecutive days with at least 0.25 inches (6.4 mm) of precipitation. From the 15th through the 18th, Roanoke, VA (1912-2018) and Asheville, NC (1869-2018) observed and tied their longest streak of 4 consecutive days with at least 1 inch (25.4 mm) of precipitation, respectively. Seventeen long-term stations across the region observed their highest 1-day precipitation total on record for May, including Grandfather Mountain, NC (1956-2018; 7.74 inches, 197 mm), Clayton 1 SSW, GA (1894-2018; 6.10 inches, 155 mm), Wilmington, NC (1871-2018; 5.52 inches, 140 mm), Lake City 2 E, FL (1893-2018; 5.12 inches, 130 mm), and Richmond, VA (1887-2018; 3.86 inches, 98.0 mm). During the week of the 13th through the 19th, a slow-moving low pressure system produced 5 to more than 10 inches (127 to more than 254 mm) of rainfall across broad portions of central and southern Florida, western North Carolina, and south-central and eastern Virginia. On the 18th, several rock slides and mudslides were reported in the mountains of western North Carolina, with one woman killed after her home was crushed by a debris flow in Polk County. Numerous roads in portions of North Carolina and Virginia were washed out by floodwater, while two families in Caldwell County, NC had to be rescued by helicopter from the roofs of their flooded homes. From the 22nd through the 24th, several rounds of slow-moving thunderstorms generated 5 to 10 inches of rainfall across portions of west-central Georgia (including the Columbus metropolitan area) and east-central Alabama. Talbotton, GA (1893-2018) and Thomaston 4 SE, GA (1956-2018) observed their second and fifth highest 1-day precipitation total for any month on record, with 8.57 and 5.42 inches (218 and 138 mm), respectively. Numerous flooded roads and overtopped bridges were reported in these areas, with several bridges collapsing in Smiths Station, AL. Around 4:00 PM CDT on the 28th, Subtropical Storm Alberto made landfall near Laguna Beach, FL with maximum sustained winds of 45 mph. From the 26th through the 30th, Alberto produced 3 to more than 10 inches (76.2 to more than 254 mm) of rainfall in portions of Alabama, the Florida Panhandle, south-central and northeastern Georgia, Upstate South Carolina, and western and southeastern North Carolina. Significant flash flooding occurred across western North Carolina and northeastern Georgia, resulting in numerous mudslides, road closures (including Interstate 40), evacuations, and swift water rescues. On the 28th, two journalists, who were preparing to cover the impacts of Alberto in an area damaged by flooding and mudslides earlier in May, were killed when a tree fell onto their vehicle in Polk County, NC. On the 30th, a landslide destroyed a home in Watauga County, NC, killing two people who were inside.
- There were 328 severe weather reports across the Southeast during May, which is less than 75 percent of the median monthly frequency of 452 reports during 2000-2017. About 80 percent (267 of 328) of the severe weather reports during the month were for strong thunderstorm winds, and nearly half (122 of 267) of these reports occurred in Virginia. At least one severe weather report was recorded on 23 days during the month, but about half (161 of 328) of the reports occurred on just two days (10th and 14th). On the 14th, a vigorous squall line (nearly meeting the criteria for a derecho) produced significant wind damage and caused tens of thousands of power outages across portions of northern and eastern Virginia, as well as Washington, D.C. Numerous homes and vehicles were damaged by fallen trees, but there were no reports of injuries or fatalities. Some of the highest recorded wind gusts included 64 mph at a mesonet station near Richmond, 63 mph at Manassas Regional Airport, and 58 mph at Washington Dulles International Airport. A total of 8 tornadoes (1 unrated, 6 EF-0s, 1 EF-1) were confirmed across the region, which is slightly less than the median frequency of 11 tornadoes observed during May. On the 11th, a female middle school teacher was injured by a lightning strike at a YMCA outdoor camp in Greenville County, SC. On the 16th, a 53-year-old woman was killed and two others were injured by a lightning strike while working on a produce farm in Parkland, FL.
- During the first half of May, moderate-to-severe (D1-D2) drought covered approximately 15 percent of the Southeast, as above-average temperatures and below-normal precipitation were observed across much of the region. On May 8th, over 25 percent of Florida, Georgia, and South Carolina were classified in moderate-to-severe drought, with localized portions of Alabama, North Carolina, and Virginia in moderate drought. However, well-above-normal precipitation during the second half of the month rapidly eliminated drought conditions from the region. A prevalence of warm, dry weather during the first half of May allowed farmers to resume crop planting and other field activities, which were significantly delayed by unusually cool temperatures in March and April. However, a prolonged lack of rainfall and insufficient soil moisture in some portions of the region prevented crop planting and slowed the growth of livestock pastures and hayfields. The persistence of low humidity from March through mid-May reduced disease pressure on fruit and vegetable crops across North Carolina, with a good yield of blueberries expected for the sixth largest producer in the nation. While below-average temperatures in March and April reduced the quantity of the largest Vidalia onion sizes, favorable weather conditions during late April and May resulted in a near-perfect harvest of the onion crop in southeastern Georgia. During the second half of the month, persistent rainfall replenished soil moisture levels in crop fields and livestock pastures across much of the region, but heavy precipitation and flooding in some areas prevented fieldwork, increased disease pressure on crops, and required fields to be replanted. The quality of small grains (e.g., wheat, rye, and oats) and hay deteriorated due to lodging (i.e., when high winds or heavy rain cause crops to fall over) and excessive dampness, with many farmers unable to harvest these crops from wet or flooded fields.
- For more information, please go to the Southeast Regional Climate Center Home Page.
- High Plains Region: (Information provided by the High Plains Regional Climate Center )
- The cool temperatures experienced in April by eastern portions of the region were quickly forgotten in May, as a drastic warmup brought summerlike temperatures to the High Plains. Departures across the Dakotas, Nebraska, and Kansas ranged from 4.0-10.0 degrees F (2.2-5.6 degrees C) below normal in April to 4.0-10.0 degrees F (2.2-5.6 degrees C) above normal in May. The extremes were evident in locations such as Aberdeen, South Dakota, which went from having its 2nd coolest April to having its 3rd warmest May. This rapid change in temperatures impacted agriculture and livestock. For instance, warmer temperatures aided with crop progress after slow growth in April, but increased evaporative demand worsened winter wheat conditions in Colorado and Kansas where it has been dry since the fall. Additionally, oppressive heat and humidity in late May caused cattle deaths in South Dakota because the cattle were not yet acclimated to these conditions. Looking at temperatures for the spring season, Colorado was particularly warm, as departures were generally 2.0-4.0 degrees F (1.1-3.3 degrees C) above normal. Alamosa, Colorado Springs, and Pueblo each had a top 10 warmest spring on record.
- As for precipitation, conditions varied across the region, as wetter areas included a swath from western Wyoming eastward into central Nebraska and Kansas, while the rest of the region was dry. Heavy rains improved drought conditions throughout a large part of Kansas and northeastern Colorado, while continued dryness caused drought to spread and intensify across portions of the Dakotas. A combination of snowmelt and heavy rains caused flooding in the Upper Missouri Basin, and a statewide flooding emergency was declared in Montana. Like May, spring precipitation varied throughout the High Plains, and records for wetness and dryness were both set. For instance, this spring was among the top 10 wettest for Scottsbluff, Nebraska and Akron, Colorado, while it was among the top 10 driest for Alamosa, Colorado; Pueblo, Colorado; Salina, Kansas; and Aberdeen, South Dakota.
- A stark turnaround in temperatures occurred in May, as the cool pattern experienced by eastern portions of the High Plains in April abruptly ended and above-normal temperatures prevailed. Average temperatures in May ranged from approximately 3.0-9.0 degrees F (1.7-5.0 degrees C) above normal, with the highest departures occurring throughout much of Kansas and eastern areas of the Dakotas, Nebraska, and Colorado. Many locations had a top 10 warmest May on record, some of which followed a top 10 coolest April. Locations that had their warmest May on record included Concordia, KS; Dodge City, KS; Topeka, KS; Colorado Springs, CO; and Pueblo, CO.
- In addition to average monthly temperatures, numerous daily records for maximum temperatures were broken as well. Temperatures reached 90.0 degrees F (32.2 degrees C) on quite a few days throughout a large portion of the High Plains, with several locations setting new records or ranking in the top five for most number of days that 90.0 degrees F (32.2 degrees C) was reached in the month of May. For instance, Dodge City, KS and Salina, KS reached 90.0 degrees F (32.2 degrees C) on 15 out of 31 days in May, which was the most on record for both locations.
- The highest temperatures of the month occurred over Memorial Day Weekend for most of the High Plains and caused negative impacts. Temperatures reached 100.0 degrees F (37.8 degrees C) in portions of Nebraska and South Dakota. Daily record highs were set four days in a row (25th-28th) in Omaha, Nebraska, which buckled pavement and compromised air quality in and around the area. This impressive heat wave was also blamed for cattle deaths in South Dakota.
- Both wet and dry conditions existed in the High Plains during May. Precipitation was 150-300 percent of normal across much of Wyoming, the western half of Nebraska, northeastern Colorado, and pockets of Kansas and the Dakotas. Locations that received enough precipitation to make the top 10 of wettest Mays on record included North Platte, Nebraska (4th wettest); Scottsbluff, Nebraska (5th wettest); and Goodland, Kansas (6th wettest). The rest of the region remained dry in May, particularly southwestern Colorado and eastern South Dakota where precipitation was less than 50 percent of normal. Aberdeen, South Dakota had its 7th driest May on record with only 17 percent of normal precipitation.
- The cool and dry conditions of April brought about a slow start to the severe weather season in the High Plains, but the pattern change allowed for all modes of severe weather to occur in May, impacting parts of the region. For instance, a storm dropped hail that was 2.0 inches (5 cm) in diameter in Scott County, Kansas on the 14th, damaging wheat fields, windows, siding, and fertilizer tanks. According to Kansas Wheat, Scott City and Sharon Springs were hardest hit. On the 17th-18th, another storm brought torrential rainfall to north-central South Dakota, which caused flash flooding. The flooding destroyed a concrete dam at Lake Hiddenwood Recreation Area in Walworth County. On Memorial Day (May 28th), heavy rain fell in Graham County, Kansas, with 5.61 inches (142 mm) reported at the Hill City Municipal Airport. The rain washed out roads and caused the Saline River to flood.
- One positive impact of the heavy rains that fell in parts of the region was it helped improve soil moisture conditions. Soil moisture conditions are very important during this time of year, as most crops have been planted and the moisture is needed for them to grow. According to the U.S. Department of Agriculture Weekly Weather and Crop Bulletin, beneficial rains improved topsoil and subsoil moisture in May in portions of Colorado, Kansas, North Dakota, and Nebraska. However, topsoil moisture declined in South Dakota, where most areas missed out on heavy rainfall and experienced much-above-normal temperatures. The decline of topsoil moisture is an indicator of worsening drought conditions, and it is something to watch closely as we move into the season when crop water demand is highest.
- Upper Missouri Basin snowpack peaked in April and rapidly declined in May. According to the U.S. Army Corps of Engineers, Snow Water Equivalent (SWE) above Fort Peck Reservoir was 96 percent of average as of the end of May, and SWE between Fort Peck and Garrison Reservoirs was 95 percent of average. Above-normal temperatures caused the snowpack to melt quickly and, as a result, streamflows ran high throughout Wyoming and Montana. According to the U.S. Army Corps of Engineers Missouri River Water Management Division in Omaha, Nebraska, the Corps intends to continue above-average releases from all system projects throughout the summer in order to slowly evacuate stored flood waters. Meanwhile, streamflows were below normal in areas of Kansas and Colorado where drought was present.
- Both improvements and degradations in drought conditions occurred throughout the High Plains in May. According to the U.S. Drought Monitor, little change occurred to the region-wide percent area experiencing drought over the past month. However, changes in conditions were evident on a more local basis. For instance, heavy rains improved conditions across portions of Kansas, northern Colorado, and south-central Nebraska, while drought expanded and intensified in the Dakotas, southern Colorado, and southeastern Nebraska.
- Kansas experienced the greatest improvements in drought conditions during the month of May. Portions of central Kansas received up to 300 percent of normal precipitation, which was quite welcome after paltry amounts in April. Unfortunately, it was too late to improve winter wheat conditions in Kansas, as nearly half of the crop was still in poor to very poor condition by the end of the month.
- Meanwhile, continued dryness and high temperatures caused drought to expand and intensify in the Dakotas and parts of Colorado and Nebraska. In North Dakota, pastures were dry and low streamflows impacted flow releases from dams. Twenty-one counties were declared natural disaster areas due to lingering drought conditions that caused significant production losses last year. Impacts continued to mount in Colorado, as livestock producers reduced herds and hauled water, and visitation declined in Great Sand Dunes National Park due to low flows in Medano Creek.
- For more information, please go to the High Plains Regional Climate Center Home Page.
- Southern Region: (Information provided by the Southern Regional Climate Center)
- May temperatures were above normal throughout most of the Southern Region. Western Oklahoma and northern Texas experienced temperatures 8 to 10 degrees F (4.44 to 5.55 degrees C) above normal. Most of Arkansas, Tennessee, and Oklahoma, northern, central and western Texas, northern Louisiana, and northern and central Mississippi experienced 4 to 8 degrees F (2.22 to 4.44 degrees C) above normal. There were only a few areas in southwest Texas that experienced slightly below normal temperatures. The statewide monthly average temperatures were as follows: Arkansas—74.80 degrees F (23.78 degrees C), Louisiana—77.50 degrees F (25.28 degrees C), Mississippi—75.80 degrees F (24.33 degrees C), Oklahoma—74.90 degrees F (23.83 degrees C), Tennessee—72.20 degrees F (22.33 degrees C), and Texas—77.90 degrees F (25.50 degrees C). The statewide temperature rankings for May were as follows: Arkansas (first warmest), Louisiana (third warmest), Mississippi (fourth warmest), Oklahoma (first warmest), Tennessee (second warmest), and Texas (second warmest). The region as a whole had its warmest May on record. All state rankings are based on the period spanning 1895-2018.
- Precipitation values for the month of May varied spatially throughout the Southern Region. Eastern Tennessee received 200—400 percent of normal precipitation. Parts of northwestern Oklahoma, northern and central Texas, southwestern Mississippi and south central Tennessee received 150—200 percent of normal precipitation. Areas in Western Tennessee, northeastern and southeastern Mississippi, southern and central Texas, and southern Oklahoma received 125—150 percent of normal precipitation. In contrast, parts of northwestern and western Texas received 5 percent or less of normal precipitation. Areas of central, western, eastern, and southern Texas, southwestern Oklahoma, southern and eastern Arkansas, east central Mississippi, and most of Louisiana received 50 percent or less of normal precipitation. The state-wide precipitation totals for the month were as follows: Arkansas—3.29 inches (83.57mm), Louisiana—2.02 inches (51.31 mm), Mississippi—3.58 inches (90.93 mm), Oklahoma—4.05 inches (102.87 mm), Tennessee—4.82 inches (122.43 mm), and Texas—2.04 inches (51.82 mm). The state precipitation rankings for the month were as follows: Arkansas (twenty-third driest), Louisiana (tenth driest), Mississippi (forty-fifth driest), Oklahoma (forty-eighth driest), Tennessee (forty-eighth wettest), and Texas (nineteenth driest). All state rankings are based on the period spanning 1895-2018.
- At the end of May, exceptional and extreme drought classifications are still present throughout parts of western Oklahoma and northern Texas. Severe drought classifications are present throughout parts of southwestern, southeastern, and northern Texas and western and northern Oklahoma. The moderate drought classification remains throughout parts of western, central, northern, and southeast Texas. Moderate drought classification appeared in northeastern and southwestern Texas and in extreme southeastern Louisiana. There are currently no drought conditions in Arkansas, Mississippi, and Tennessee.
- On May 2, 2018, there were five tornadoes reported throughout Oklahoma and Texas. There were reports of golf ball sized hail in Sonora, Texas. In Frederick, Oklahoma a wind gust of 106 mph (170.59 kph) was reported.
- On May 3, 2018, a tornado in Byng, Oklahoma, destroyed two trailer homes and one brick home had siding and roof damage. In Meg, Arkansas, an EF-1 tornado damaged two chicken houses. In Alba, Texas, strong wind caused a horse trailer to roll into a tree.
- On May 5, 2018, strong winds caused downed trees and broken windows in Bangham Village, Tennessee.
- On May 6, 2018, a 67 mph (107.83 kph) wind gust was reported in Carlisle and Stuttgart, Arkansas.
- On May 8, 2018, a 75 mph (120.70 kph) wind gust caused damage to fences, roofs, windows, and trees in Memphis, Texas.
- On May 13, 2018, baseball sized hail was reported in Glazier, Texas, and golf ball to lemon sized hail was reported in Estelline, Texas.
- On May 14, 2018, an 81 mph (130.36 kph) wind gust was reported in Gould, Oklahoma.
- On May 15, 2018, hen egg sized hail was reported by the county sheriff in Miami, Texas and wind driven hail caused heavy roof and siding damage in Crosbyton, Texas.
- On May 16, 2018, baseball sized hail was reported in Big Spring, Texas.
- On May 17, 2018, a tornado was reported in Monette, Arkansas, and hen egg sized hail was reported in Borger, Texas.
- On May 18, 2018, strong winds caused downed trees in Alcoa, Tennessee. In New Orleans, Louisiana, strong winds caused damages to the performance stage and booths at the Bayou Boogallo on Bayou Street.
- On May 19, 2018, a tornado was reported in Pawhuska, Oklahoma. In Gageby, Texas, hail caused damage to a skylight and a windshield. Strong winds blew over large trees, snapped large tree limbs, and damaged a home in Vinita, Oklahoma.
- On May 20, 2018, a tornado damaged homes and demolished an above ground pool in Leander, Texas.
- On May 23, 2018, hail damaged over 20 vehicles in Orla, Texas. Strong winds damaged a store front in Tulsa, Oklahoma.
- On May 25, 2018, a tornado was reported in Pontotoc, Texas. Baseball and softball sized hail was reported in De Leon, Texas. A 72 mph (115.87 kph) wind gust was reported in Goodlett, Texas.
- On May 27, 2018, baseball sized hail was reported in Pampa, Texas; an 80 mph (128.75 kph) wind gust was reported in Kingsmill, Texas.
- On May 28, 2018, a tornado damaged a barn in Goodwell, Oklahoma.
- On May 29, 2018, a tornado was reported in Mobeetie, Texas. Tennis ball sized hail was reported in Camp Houston, Oklahoma.
- On May 30, 2018, strong winds caused all windows to be blown out of the north side of a home in Higgins, Texas, and a 76 mph (122.31 kph) wind gust was reported in Camargo, Oklahoma.
- For more information, please go to the Southern Regional Climate Center Home Page.
- Western Region: (Information provided by the Western Region Climate Center)
- An active weather pattern this month brought above normal precipitation to the Great Basin and Intermountain West. Temperatures were near normal across much of California, the Great Basin, and Arizona. In contrast, much warmer than normal and in many cases, record breaking, temperatures were observed across the Northwest as well as in New Mexico and Colorado.
- Several closed low-pressure systems impacted the West during May. These systems contributed to above normal precipitation, much of it in the form of thunderstorms and intense rainfall, over the Sierra Nevada, Great Basin, and portions of the Inland Northwest. Reno, Nevada, reported 1.84 in (47 mm) of precipitation, 375% of normal and the 4th wettest May since records began in 1937. High intensity rainfall produced a debris flow on a recently burned area near Topaz Lake (south of Reno), covering both lanes of US Route 395 near the California-Nevada border in roughly two feet (~0.6 m) of sediment. Further east, Elko Nevada, observed 2.22 in (56 mm), 231% of normal, which was the 11th wettest May in a 131-year record. In eastern Idaho, Idaho Falls logged 2.13 in (54 mm), 131% of normal precipitation. In south-central Montana, Billings reported 5.22 in (133 mm), 239% of normal and the 4th wettest May since records began in 1934. There were only small areas of drought amelioration in the West this month in central Idaho, northeastern Montana, northern Colorado, and northeastern New Mexico. The areas that received above normal precipitation were generally not experiencing significant drought conditions and rely primarily on the snowpack for water resources. In many areas, May precipitation acted to increase surface soil moisture but did little to offset deficits in snowpack accrued during the winter and early spring season. At many mid-to-low elevation locations in the Sierra Nevada, Oregon Cascades, Wasatch, and Great Basin ranges, snowpack completely melted out in May, which is 2-4 weeks earlier than normal.
- Dry conditions dominated along the West Coast and across the southern border of the region. Seattle, Washington, received only 0.12 in (3 mm) of precipitation, tie with 1992 for the driest May in a 74-year record. San Jose, California, reported no measurable precipitation this month, as with 24 other years in the stations 126-year record. Further south, Tucson, Arizona, also reported no measurable precipitation, same as 27 other years in the station's record beginning in 1946. Drought conditions worsened across much of the Southwest this month in the US Drought Monitor, especially in Arizona and New Mexico. Much of the Four Corners region is currently experiencing extreme to exceptional drought. Severe drought was also introduced this month in eastern Oregon.
- Temperatures were well above normal across the northern portion of the West. In central Washington, Wenatchee reported an average May temperature of 66.3 F (19.1 C), 6.5 F (3.6 C) above normal and the warmest May since records began in 1959. In northeastern Montana, the average May temperature at Glasgow was 62.7 F (17.1 C), 7.6 F (4.2 C) above normal, the warmest in a 71-year record. Above normal temperatures contributed to rapid snowpack melt and flooding in this region. Portions of New Mexico and Colorado also experienced well above normal temperatures. The average May temperature for Tucumcari, New Mexico, was 73.4 F (23 C), 7.5 F (14.2 C) above normal and the warmest since records began in 1948.
- May temperatures were near normal across Alaska, while several locations received well above normal precipitation. In the Interior, Bettles observed its second wettest May in a 68-year record at 2.44 in (62 mm), 277% of normal. As normal May precipitation is fairly low, this above normal precipitation did not result in flooding. The mean extent of May sea ice in both the Bering and Chukchi Seas was the lowest in 40 years of data. Further south, May precipitation was variable across Hawaii, though favored windward areas. For example, Hana, on the eastern side of Maui, reported 7.33 in (186 mm) of rainfall, 131% of normal. The leeward areas of Maui, Big Island, Oahu, and Molokai experienced a dry spring, prompting the introduction of abnormally dry conditions this month in the US Drought Monitor.
- May (all month): Snowmelt Flooding in some areas of the Northwest: Record snowpack in the Pacific Northwest and western Canada combined with a period of above normal temperatures and, in some cases, compounded by above normal May precipitation, has contributed to flooding in this region. The governor of Montana declared a statewide flood emergency this month. In Missoula, over 60 homes were evacuated along the Clark Fork River, which reached major flood stage for the first time since 1981. Heavy rains in south-central Montana led to flood issues on the Yellowstone and Clarks Fork of the Yellowstone River. North-central Washington also experienced flooding, notably along the Okanogan River. On May 10, the Washington governor declared a State of Emergency for 20 central and eastern Washington counties due to flooding.
- May (all month): High fire danger in Southwest: In southwestern Utah, officials declared the fire season as beginning on May 16, two weeks earlier than is usual. A dry winter and spring combined with windy conditions have dried out vegetation, creating fire hazard. In Arizona, Coconino National Forest was closed due to high fire danger, impacting recreational activities. The Tinder Fire, which began in late April due to an illegal campfire in the Coconino National Forest, destroyed 33 homes and burned over 16,000 acres (6475 hectares) by late May.
- For more information, please go to the Western Regional Climate Center Home Page.
Citing This Report
NOAA National Centers for Environmental Information, State of the Climate: National Climate Report for May 2018, published online June 2018, retrieved on September 17, 2019 from https://www.ncdc.noaa.gov/sotc/national/201805/.