National Overview - December 2015
NCEI added Alaska climate divisions to its nClimDiv dataset on Friday, March 6, 2015, coincident with the release of the February 2015 monthly monitoring report. For more information on this data, please visit the Alaska Climate Divisions FAQ.
Maps and Graphics
Temperature and Precipitation Ranks
U.S. Percentage Areas
- Climate Highlights — December
- The average contiguous U.S. temperature during December was 38.6°F, 6.0°F above the 20th century average. This was the warmest December on record for the Lower 48. This bested the previous record of 37.7°F set in 1939. The average maximum (daytime) temperature was 48.1°F, 5.3°F above the 20th century average, the second highest maximum value on record behind 1939. The average minimum temperature was 29.2°F, 6.6°F above average. This bested the previous record set in 2014.
- Record warmth engulfed the eastern half of the nation, where 29 states had the warmest December on record. Near- to below-average December temperatures were observed in the West. No state was record cold.
- Both maximum and minimum temperatures were record and near-record high for the eastern half of the nation. Maximum and minimum temperatures were near- to below average across the West.
- Alaska had its 28th warmest December on record with a temperature of 7.7°F, 4.0°F above average. Western and central parts of Alaska were warmer than average, while much of eastern Alaska had near-average December temperatures.
- During December, there were 18.8 times more record warm daily maximum and minimum temperature records compared to cold daily maximum and minimum temperature records. There were 11,981 warm daily temperature records (5,215 maximum and 6,766 minimum) compared to 635 cold daily temperature records (371 maximum and 264 minimum).
- Based on NOAA's Residential Energy Demand Temperature Index (REDTI), the contiguous U.S. temperature-related energy demand during December was zero, which was much below the average of 51.9. This tied the lowest REDTI on record in 2006. The record warmth in the densely populated Midwest and Northeast contributed to the record low REDTI.
- The December precipitation total for the contiguous U.S. was 3.93 inches, 1.58 inches above the 20th century average, ranking as the wettest December on record. This surpassed the previous record of 3.76 inches set in 1982. December 2015 marks the only month in the 121-year period of record that holds the title of both warmest and wettest month on record.
- Above-average precipitation was observed across the country, with 23 states being much wetter than average. Iowa had its wettest December with 4.49 inches of precipitation, 3.38 inches above average. Wisconsin was also record wet with 4.22 inches of precipitation, 2.95 inches above average.
- A strong low pressure system moved through the central U.S. near the end of December causing record flooding, severe weather, and heavy snowfall. Record crests and overtopped levees were observed along parts of the Mississippi River and its tributaries, deadly tornadoes ripped through the Southern Plains and Mid-South and heavy snow/ice was observed from the Southern Rockies to Midwest and New England. This storm system resulted in at least 50 fatalities across the country — the deadliest weather event of 2015 — and caused over billion dollars in losses, according to preliminary estimates.
- According to the December 29th U.S. Drought Monitor report, 18.7 percent of contiguous U.S. was in drought, down from 20.6 percent at the beginning of the month. Drought conditions dramatically improved across the Pacific Northwest, where record and near-record precipitation was observed during December. Drought also improved in parts of the Central Plains and Upper Midwest. Drought conditions expanded in parts of the Great Lakes and Northeast.
**A comparison of the national temperature departure from average as calculated by NCDC's operational dataset (nClimDiv), the U.S. Historical Climatology Network (USHCN), and the U.S. Climate Reference Network (USCRN) is available on our National Temperature Index page.**
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 Climatic Data Center.
- Northeast Region: (Information provided by the Northeast Regional Climate Center)
- December was an extremely mild month as the Northeast was record warm. The region's average temperature of 40.2 degrees F (4.6 degrees C) was 11.8 degrees F (6.6 degrees C) above normal. All twelve states were also record warm, with departures ranging from 9.7 degrees F (5.4 degrees C) above normal in Maine to 12.7 degrees F (7.1 degrees C) above normal in New Jersey. Of the region's 35 major airport climate sites, 34 sites were record warm. More than 300 daily maximum and high minimum temperature records were set or tied. Albany, New York and Burlington, Vermont had their highest temperatures ever recorded during meteorological winter with highs of 72 degrees F (22 degrees C) and 68 degrees F (20 degrees C), respectively, on December 24.
- The region received 4.52 inches (114.81 mm) of precipitation in December, or 130 percent of normal. This made it the 20th wettest December on record. Eleven states were wetter than normal, with three ranking the month among their top 20 wettest: Vermont, 12th wettest; Maine, 15th wettest; and New Hampshire, 19th wettest. Precipitation for all states ranged from 99 percent of normal in Connecticut to 146 percent of normal in Maine.
- In early December, 20 percent of the Northeast was abnormally dry, with another 6 percent of the region experiencing moderate drought. Conditions deteriorated somewhat during December, with abnormal dryness expanding to cover 31 percent of the region by month's end.
- Mild temperatures led to below-normal snowfall for the entire region. In fact, several upstate New York sites had their least snowy Decembers on record. Some of those sites also had their latest measurable snow and/or their latest first inch of snow. Across the Northeast, transportation departments performed roadwork and continued construction projects longer into the season, as well as saved money on snow removal, fuel, and personnel costs. Home heating costs were also down, in part due to the warm weather. While some golf courses saw an increase in business, winter recreation spots and winter gear retailers experienced decreased business. In fact, many ski resorts opened late, suspended operations, or had limited trails open. The Mount Washington Auto Road in New Hampshire opened for guided auto tours in late December for the first time in (at least) 35 years. The warmth allowed some crops such as lettuce to be harvested later into December, but caused other plants such as viburnum to bloom early. In addition, insects continued to thrive and the allergy season was prolonged in several areas. There was one lake-effect event in December. From the 19th to 20th, up to 3 feet (1 m) of snow fell east of Lake Ontario and up to a foot (0.3 m) of snow fell east of Lake Erie.
- For more information, please go to the Northeast Regional Climate Center Home Page.
- Midwest Region: (Information provided by the Midwest Regional Climate Center)
- December was unseasonably warm across the Midwest and ranked as the warmest December on record in the past 121 years (1895-2015). All nine Midwest states also experienced their warmest December on record. Across the Midwest, temperatures were at least 6 degrees F (3.3 C) above normal, with some portions of Wisconsin, eastern Ohio, and eastern Kentucky up to 12 degrees F (6.7 C) above normal. The preliminary region wide December temperature was 36.7 degrees F (2.6 C), which was 10.7 degrees F (5.9 C) above normal and 2.6 degrees F (1.4 C) above the previous record set in 1923. Several record daily high temperatures were broken throughout the month. A slew of records were broken across the region between December 12th and 14th, with some locations recording 70 degrees F (21 C) or higher during this time. The end of the month also saw significantly above normal temperatures, with the majority of Kentucky and southeast Ohio recording temperatures between 65 degrees F (18 C) and 77 degrees F (25 C) on December 27th. The 2015 average annual temperature for the Midwest averaged near- to slightly above-normal across a majority of the region, but temperatures fluctuated from below-normal (winter, summer) to above-normal (fall, December) throughout the year.
- Not only was it the warmest December on record for the Midwest, but it was also the wettest December (1895-2015). The preliminary region wide December precipitation was 5.01 inches (127 mm), which was 2.80 inches (71 mm) above normal and well above the previous record of 4.42 inches (112 mm) set in 1982. Monthly precipitation totals ranged from 0.5 inches (13 mm) in northwest Minnesota to 10-25 inches (254-635 mm) across portions of Missouri. With the exception of northwest Minnesota, monthly totals were above normal for the region. Precipitation was twice the normal amount across much of Illinois, Wisconsin, Iowa, and Missouri with some locations in Iowa receiving four to five times the normal December precipitation. For individual states, Iowa and Wisconsin experienced their wettest December on record. Illinois, Missouri, and Minnesota experienced their second wettest December on record, while all other Midwest states ranked among the top eight wettest. Despite well-above normal precipitation, the unseasonably warm temperatures in December meant below-normal snowfall for much of the region in December. Snowfall in portions of Upper Michigan was as much as 20 inches (51 cm) to 40 inches (102 cm) below normal. On the other hand, southwest Minnesota, northwest Minnesota, and northwest Iowa received snowfall that was 5 inches (13 cm) to 15 inches (38 cm) above normal. 2015 was the second wettest year on record for the Midwest, with a region wide annual precipitation total of 42.59 inches (1,082 mm). The wettest months of the year were May, June, and December.
- After a wet December, drought concerns remained minimal across the Midwest. At the beginning of December, only 3.16 percent of the region was in drought and by the end of the month, this reduced to 2.35 percent. The main area of improvement was in the Upper Peninsula of Michigan. On the other hand, a small portion of northeast Ohio remained in moderate drought. Other drought areas that did not see much improvement in December were portions of central Indiana, northern Indiana, and southern Michigan.
- The most notable event of the month occurred from the 26th to the 29th. This storm system brought heavy snowfall to Iowa, Minnesota, Wisconsin, and northern Michigan while at the same time, torrential rainfall to areas further south in Missouri, Illinois, and western Kentucky. The torrential rainfall caused widespread moderate to major flooding in Illinois and Missouri, and moderate flooding to parts of Kentucky and Indiana. Some of the worst flooding occurred in Missouri where local rainfall amounts for the 3-day period reached 9-11 inches (229-279 mm) in St. Louis and St. Charles counties in Missouri. Flash flooding was widespread in Missouri, resulting in hundreds of water rescues and major transportation impacts as portions of major interstates and railroads were closed for a period of time. Unfortunately, this historic flood claimed the lives of at least fifteen people in Missouri and nine in Illinois.
- 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 exceptionally above average across the Southeast region, with numerous record-breaking extremes observed during December. Mean temperature departures were 9 to 14 degrees F (5 to 7.8 degrees C) above average across the entire region except southern Florida, where monthly departures ranged from 6 to 9 degrees F (3.3 to 5 degrees C) above average. A total of 53 out of 70 long-term (i.e. period of record exceeding 100 years) stations across the region, including those in nearly all major cities, observed or tied their warmest December mean temperature on record. In addition, every state in the region had at least one reporting station with a 49-year period of record or greater that observed its warmest daily maximum temperature for December on record and at least one station that observed its warmest daily minimum temperature for December on record. The exceptional warmth was also very persistent during the month, as Savannah, GA (1874-2015) and Jacksonville, FL (1871-2015) observed their greatest count of December days on record (24 and 14 days, respectively) with a maximum temperature at or above 70 (21.1 degrees C) and 80 degrees F (26.7 degrees C), respectively. On 6 days during the month (25th and 27th-31st), Key West, FL (1872-2015) observed its warmest minimum temperature (79 degrees F; 26.1 degrees C) for December on record. Temperatures were well above average in Puerto Rico and the U.S. Virgin Islands, as San Juan, PR (1898-2015) tied its fifth warmest December mean temperature on record. The warmest weather of the month occurred from the 24th through the 27th, as an unseasonably strong subtropical high developed off the Atlantic coast. During this 4-day period, maximum temperatures exceeded 70 degrees F and minimum temperatures remained above 60 degrees F (15.6 degrees C) across much of the region. On the 24th, Norfolk, VA (1874-2015) observed its warmest December maximum temperature on record (82 degrees F; 27.8 degrees C). On the same day, Wilmington, NC (1873-2015) and Washington D.C. (1872-2015) observed their warmest December minimum temperature on record at 72 degrees F (22.2 degrees C) and 60 degrees F, respectively. In contrast, the coldest weather of the month occurred from the 19th through the 20th, as a continental high pressure system settled over the region. Daily minimum temperatures fell below 30 degrees F (-1.1 degrees C) across much of the region north of Florida, with a few locations reaching the upper teens F (-8.3 to -7.2 degrees C).
- Precipitation was well above normal across much of the Southeast region during December, with numerous extremes recorded. The wettest locations, where monthly precipitation totals ranged from 200 to 600 percent of normal, were found across Alabama, Georgia (except the southeastern quadrant), northern portions of South Carolina, North Carolina, south-central Virginia, the Florida Panhandle, and southern Florida. At least one long-term (period of record exceeding 100 years) station in every state, except for Virginia, observed its wettest December on record. Columbus, GA (1893-2015) observed its all-time wettest month on record with 17.38 inches (441 mm) of precipitation. As the wettest reporting station across the region during the month, Clayton, AL (1956-2015) observed its wettest December on record and third wettest month all time with 21.21 inches (539 mm) of precipitation. On the 25th, Haleyville, AL (1936-2015) reported its wettest December day on record with 7.80 inches (198 mm) of precipitation. In contrast, the driest locations were found across central and northern Florida as well as southeastern Georgia, where monthly precipitation totals were between 5 and 50 percent of normal. Precipitation was also well below normal across much of Puerto Rico and the U.S. Virgin Islands, with monthly precipitation totals that were less than 5 percent of normal across southwestern Puerto Rico. Ensenada, PR (1955-2015) tied its driest December on record with no measurable precipitation.
- There were 59 severe weather reports across the Southeast during December, which is very close to the median monthly frequency of 57 reports during 2000-2014. Approximately 70 percent of these reports were for damaging thunderstorm winds, and about 25 percent of the reports were for tornadoes. At least one severe weather report was recorded within the region on 10 days during the month. On the 17th, the roof of a school building at Central Hamilton Elementary School in Jasper, FL was blown off by strong thunderstorm winds, but no injuries were reported. On the 23rd, two inch (hen egg-sized) hail was reported with a severe thunderstorm near downtown Mobile, AL. Nine tornadoes (6 EF-0s, 1 EF-1, 2 EF-2s) were confirmed across the region during the month, which is equal to the short-term (2000-2014) median frequency of tornadoes observed during December. During a severe weather outbreak centered northwest of the region on the 23rd, an EF-2 tornado touched down in Lauderdale County, AL and damaged three single family homes, one mobile home, and a church. One resident was injured when the tornado blew off nearly the entire roofing structure of their house. Two days later, another EF-2 tornado damaged about 50 homes, two of which were completely destroyed, and injured two people in Midfield, AL, a town located less than 10 miles from downtown Birmingham.
- Drought conditions (D1 and greater) were not observed across the Southeast region (excluding Puerto Rico) during December. The extent of severe-to-extreme (D2 and D3) drought conditions across eastern Puerto Rico decreased about 2 percent during the month, reaching a coverage of 14 percent on December 29th. However, moderate (D1) drought expanded westward along the southern coast of Puerto Rico. Extremely warm and wet conditions resulted in widespread agricultural impacts across the region. Heavy rainfall during early December significantly damaged vegetable fields in southeastern Florida, where over 50 percent of the winter yellow squash, zucchini, and green bean crop were lost due to flooding. Saturated pecan groves in Georgia prevented farmers from harvesting a significant portion of the crop. In addition, the lack of December chill hours (i.e. hour with the temperature between 32 and 45 degrees F [0 and 7.2 degrees C]) in Georgia reduced the period of winter dormancy required for peach trees and blueberry bushes to maintain a proper growth cycle, which will likely result in lower yields in 2016.
- 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 )
- For more information, please go to the High Plains Regional Climate Center Home Page.
- Southern Region: (Information provided by the Southern Regional Climate Center)
- As was the case with November, December was a warm month for the entire Southern Region. All six states averaged above normal temperatures, with all states but Texas ranking in the top three warmest Decembers on record (1895-2015). For the region as a whole, it was the third warmest December. The region-wide average temperature was 51.63 degrees F (10.91 degrees C). Temperature anomalies were highest in Mississippi and Tennessee, where most stations averaged between 8-12 degrees F (4.44-6.67 degrees C) above the monthly normal. Elsewhere, stations generally averaged between 3-5 degrees F (1.67-2.78 degrees C) across most of Texas and Oklahoma, and between 5-9 degrees F (2.78-5.00 degrees C) across most of Arkansas and Louisiana. The state-wide average temperatures for the month are as follows: Arkansas averaged 49.80 degrees F (9.89 degrees C), Louisiana averaged 59.00 degrees F (15.00 degrees C), Mississippi averaged 56.60 degrees F (13.67 degrees C), Oklahoma averaged 44.90 degrees F (7.17 degrees C), Tennessee averaged 51.20 degrees F (10.67 degrees C), and Texas averaged 51.60 degrees F (10.89 degrees C). Both Mississippi and Tennessee experienced their warmest December on record. For Arkansas, it was the second warmest December on record, while Louisiana and Oklahoma recorded their third warmest December on record. Texas experienced its sixth warmest December. All ranking records are based on the period spanning 1895-2015.
- December precipitation in the Southern Region varied spatially with some areas receiving above normal precipitation, and other areas experiencing precipitation deficits for the month. Throughout much of Louisiana and Mississippi, precipitation was near normal. This was also the case in western Tennessee and in central Texas. In southern Texas, conditions were quite dry, with many stations averaging less than half the normal precipitation.. Conversely, conditions were very wet in Oklahoma and northwestern Arkansas, where a bulk of the stations recorded between one and a half to two times the normal allotment. Similar wet conditions were also observed in eastern Tennessee. The state-wide precipitation totals for the month are as follows: Arkansas reporting 8.20 inches (208.28 mm), Louisiana reporting 5.59 inches (1414.99 mm), Mississippi reporting 7.08 inches (179.83 mm), Oklahoma reporting 4.80 inches (121.92 mm), Tennessee reporting 7.73 inches (196.34 mm), and Texas reporting 2.40 inches (60.96 mm). It was the third wettest December for Oklahoma, while Arkansas experienced their fifth wettest December. Tennessee and Mississippi recorded their fourteenth and twenty-eighth wettest Decembers on record, respectively. For Texas, it was the thirtieth wettest December and for Louisiana, the forty-fifth wettest December. All state ranking records are based on the period spanning 1895-2015.
- Near-to-above normal precipitation in the Southern Region has allowed for the continuation of drought-free conditions in all six states.
- On December 12, a tornado resulted in two injuries in Franklin County, Texas. The twister was rated as an EF-2 and 20 structures were reported damaged. To the north in Choctaw County, Oklahoma, three were injured from another twister that was also rated EF-2.
- A tornado on December 21 resulted in one injury in Rapides Parish, Louisiana. The injury resulted from an overturned trailer.
- On December 23, several tornadoes were reported in an area ranging from northern Mississippi to western Tennessee. Two fatalities were reported in Benton County, Mississippi, and two more were reported in Perry County, Tennessee. Seven more citizens were injured in Wayne County Tennessee. There were numerous reports of damage to homes in various counties from northern Mississippi to western Tennessee. Four days later on the 27th of the month, several tornadoes were reported in southern Arkansas and northern Louisiana. There were no reports of injuries or fatalities but some events did result in structural damage to homes and businesses.
- A storm on December 26 caused 12 tornadoes in the Dallas area, 7 EF-0 tornadoes, 2 EF-1, and one each of EF-2, EF-3, and EF-4. This year saw the highest number of reported tornadoes in North Central Texas 76 , beating the previous record of 73 in 1994. Prior to this event, 2015 only recorded 10 deaths due to tornado activity; 11 people lost their lives during the storm and the total damage estimated cost was 1.2 billion dollars. In addition to the tornadoes and other severe weather, Texans also experienced blizzards, snowstorms and other winter weather. El Paso, which is not known for having unusual weather, experienced white-out conditions at the Sun Bowl. The southern High Plains and Low Rolling Plains also experienced blizzard conditions. Overall, about 16 inches (406.4 mm) of snow was measured in Midland, and 10.3 inches (261.62 mm) in Lubbock with snow drifts up to 6 feet (152.4 mm). Roads closed included Interstates 10, 20 and 40 along with large numbers of state and U.S. highways. The combination of the blizzard and severe weather in North Texas made for difficult travel post-Christmas for people traveling by airplane: the weather caused 620 flights cancellations and 625 delays in the DFW International Airport along with other flight delays in smaller airports, contributing to an estimated half of all flights in and out of Texas being canceled.(Information provided by the Texas Office of State Climatology).
- By the end of the year, 2015 was the wettest year on record for Texas. The major flooding and wet periods of 2015 were in May and October. These beat the previous record from 1895. This excess rain put an end to the five year drought. The Lone Star State was drought free for all of December, with just a slight increase in the areas with Abnormal Dryness (D0) throughout the month (Information provided by the Texas Office of State Climatology).
- For more information, please go to the Southern Regional Climate Center Home Page.
- Western Region: (Information provided by the Western Region Climate Center)
- In the West, storms brought well above normal precipitation to the Northwest, northern Great Basin, and some areas of the Rocky Mountains. Temperatures averaged near normal, with pockets of above normal temperatures along the northern tier.
- The Pacific Northwest saw impressive amounts of precipitation. Portland, Oregon, observed its wettest December and all-time wettest month at 15.24 in (387 mm), 278% of normal. Portland also had its second wettest day on record on December 7, when 2.67 in (68 mm) of rain fell. Precipitation was observed in Portland each day from December 1-25, the second longest streak on record. January 1950 holds the record for longest precipitation streak at 29 days. Records for Portland began in 1938. Seattle, Washington, recorded 11.21 in (285 mm) for the month, the second wettest December in a 71-year record. McCall, Idaho, observed 7.69 in (195 mm) precipitation, 230% of normal, the 4th wettest December since records began in 1905. In the Great Basin, Ely, Nevada, logged 1.38 in (35 mm) of precipitation this month, 234% of normal, 12th wettest since records began in 1888. Pockets in the Rockies were wet as well. Hayden, Colorado, had its wettest December in a 111-year record with a total 6.68 in (170 mm) of precipitation, 415% of normal. Yosemite National Park observed 12.02 in (305 mm) of precipitation, 221% of normal and the 11th wettest since 1906. Many areas that observed above normal precipitation also saw significant snowfall. In southern Oregon, Crater Lake observed 196.7 in (500 cm) of snowfall, breaking the previous December snowfall record of 196 in (498 cm) set in 1948. Snoqualmie Pass in Washington observed its snowiest December on record at 193.3 in (491 cm) of snowfall, breaking the previous record of 192 in (488 cm) set in 1968. In the Colorado Rockies, Steamboat Springs received 66.9 in (170 cm) of snow this month, 174% of normal, 7th snowiest since records began in 1893. Snowpack in the Sierra Nevada was just slightly above normal at month's end. In the Cascades and northern Great Basin, snowpack ranged from 100% to nearly 200% of normal. The northern and central Rockies observed slightly below normal snowpack, generally 75-100% of normal, while the southern Rockies were 110% to 150% of normal. Abundant precipitation and building snowpack helped to alleviate drought conditions in eastern Washington, western Oregon, coastal northern California and portions of Idaho and Montana. Extreme to exceptional drought conditions persisted California, western Nevada, and southeastern Oregon.
- The Desert Southwest was seasonally dry this month. Las Vegas, Nevada recorded 0.01 in (<1 mm) for the month, 2% of normal. In Las Vegas's 68-year record, 16 other years observed 0.01 in (<1 mm) or less. Southern California also saw drier than normal conditions; rainfall in Los Angeles totaled 0.57 in (14 mm), 24% of normal. Drought conditions improved in a very small area of western Arizona and northern Wyoming.
- Temperatures averaged near normal across much of the West. A very cold system during the final week of the month brought temperatures 5-10 F (3-6 C) below normal across much of the West. Temperatures at a few locations across the northern tier of the region averaged above normal for December. In northeastern Washington, Chewelah recorded an average of 29.5 F (-1.4 C), 4.6 F (2.5 C) above normal. In northeastern Montana, temperatures in Glasgow averaged to 21.4 F (-5.8 C), 5.1 F (2.8 C) above normal.
- Parts of Hawaii continued to remain warm. Lihue, Kauai, had its warmest December since records began in 1950, averaging 76.2 F (24.5 C), 3 F (1.6 C) above normal. Honolulu, Oahu, and Hilo, Big Island, both had their second warmest December on record at 77.9 F (25.5 C) and 74.6 F (23.7 C), respectively. After wetter than normal conditions the past 4 months, many locations in Hawaii observed a drier than normal December. Honolulu recorded 0.27 in (7 mm), 8% of the December normal, tied for 7th driest December in 76 years. In Alaska, temperatures were within 5 F (2.8 C) of normal. With the exception of the southeast, much of the state observed drier than normal conditions this month. Fairbanks received 0.07 in (2 mm) of precipitation, 11% of normal and the 5th driest December since records began in 1929. Anchorage recorded 0.23 in (6 mm), 21% of normal, the 4th driest since records began in 1952.
- December 7-9: Flooding in western Oregon and Washington: Following a wet first week of the month, a winter storm with abundant subtropical moisture brought over 4+ in (100+ mm) of rain over a 2-day period. The heavy rains produced flooding along creeks and rivers, landslides, downed trees and power outages. Many roads in the region were closed due to landslides, disrupting travel. In Portland, Oregon, the sewer system flooded and outflowed into the Willamette River and Columbia Slough.
- December 25: Solimar Fire burns in southern California: Strong winds caused power lines to arc, igniting the Solimar Fire near Ventura, California. The fire burned 1,200 acres (486 hectares) and caused temporary closure of Highway 101. The fire could cause debris flows with coming rains.
- December 30: Disaster declared in Kootenai County, Idaho, due to snow accumulation: Kootenai County received significant snowfall this month. Coeur d'Alene observed 25 in (64 cm), more than twice its normal December snowfall. The snow placed heavy loads on trees and structures, causing branches to snap resulting in damage to several homes.
- For more information, please go to the Western Regional Climate Center Home Page.
Warm and wet conditions prevailed across much of the contiguous U.S. during the month of December. The warmth was very impressive, as nearly all states in the eastern half of the U.S. had their warmest Decembers on record, reporting temperatures of 9.0-15.0 degrees F (5.0-8.3 degrees C) above normal. There were reports of homeowners living as far north as Maryland that were still mowing their lawns. In the High Plains region, there were no statewide average temperature records broken for the month, but several individual stations reported a top 10 warmest December on record, especially in Kansas. December was not warm the entire month, however. The pattern shifted from warm to cold during the last week of December, bringing below normal temperatures to much of the region. Had it remained warm, temperature records would have been even more impressive. Record-breaking precipitation was a top story for the month as well. While only two states in the contiguous U.S. had their wettest Decembers on record, the majority of states experienced above average precipitation for the month, and there were no states that had below average precipitation. One particularly interesting aspect of the wetness was that in some places that ordinarily get snow in December, the precipitation came as rain instead. In the Northeast, many locations were far behind their normal snowfall accumulation for the season. Buffalo, New York, which is noted for its abundance of lake-effect snow, had only received 1.0 inches (2.5 cm) of snow as of the end of December, which was 35.2 inches (89 cm) below normal! The lack of cold air masses moving across the Great Lakes has minimized lake-effect snow so far this season. In the High Plains region, large areas of South Dakota, Nebraska, and Kansas experienced 400-800 percent of normal precipitation. There were so many locations that had a top 10 wettest December on record, they could not all be listed in the summary. Some notable records included Salina, KS, Lincoln, NE, and Omaha, NE (wettest); Flandreau, SD (2nd wettest); and Yankton, SD (3rd wettest).
The warm pattern continued into December for much of the High Plains region, especially in the eastern part of the area. Temperatures were as much as 3.0-9.0 degrees F (1.7-5.0 degrees C) above normal across North Dakota, Kansas, and the eastern halves of South Dakota and Nebraska. Records were especially impressive in Kansas, as several stations had a top 5 warmest December on record. Let's take a look at Salina, Kansas. It has been quite warm there since the beginning of fall. Salina just had its warmest December on record, which followed Salina's warmest fall on record (period of record 1948-2016). A particularly warm spell early in the month broke many high temperature records across the region, including Salina, which reached 71.0 degrees F (21.7 degrees C) on December 9th. Many high minimum temperature records were broken that day as well. As mentioned earlier, the warm temperatures extended the summer recreation season, such as allowing golf courses to stay open longer than normal. Other positive impacts included reduced heating needs, reduced snowfall removal costs, and the extension of the lawn mowing season, which was a positive impact for landscaping companies. However, the warm temperatures delayed the start of the winter recreation season. In Minneapolis, Minnesota, for example, a pond hockey tournament had to be rescheduled due to the unseasonably warm weather. In terms of agricultural impacts, conditions have been favorable for winter wheat, and much of the crop was in good condition as of the end of December. However, with the lack of snow cover, Arctic air masses could be damaging to the crop.
Many areas in the High Plains region experienced much above normal precipitation during December due to a persistent storm track that brought systems through the area. A large part of the region received a surplus of precipitation upwards of 4.00 inches (102 mm) with isolated pockets of up to 8.00 inches (203 mm). Records were quite impressive for December, especially in Kansas and Nebraska. As mentioned earlier, three stations had their wettest Decembers on record (Salina, KS, Lincoln, NE, and Omaha, NE). Perhaps the most notable is the precipitation that fell in Omaha. Omaha received 5.26 inches (134 mm) of precipitation in December, or 506 percent of normal, which was its wettest December on record, shattering the previous record of 4.45 inches (113 mm) in 1984 (period of record 1871-2016). In fact, Omaha had its 5th wettest year on record, recording 44.52 inches (1,131 mm) of precipitation, which was 13.90 inches (356 mm) above normal. It was an especially wet year for other parts of Nebraska too, as Scottsbluff had its 3rd wettest year on record (period of record 1893-2016), and 2015 came in as 4th wettest for Lincoln (period of record 1887-2016). December precipitation came in the form of rain, snow, and a wintry mix. Some areas even experienced thunderstorms, which is rather rare in this part of the country in December. A winter storm struck northern parts of the region December 15-16, which dropped up to 10.0 inches (25 cm) of snow in South Dakota between Sioux Falls and Brookings. Strong winds and heavy snow resulted in I-90 being closed from Chamberlain to Rapid City. Another winter storm occurred Christmas Eve, bringing several inches of snow to southern Nebraska and northwestern Kansas, which was a treat for those who were hoping for a White Christmas. The excessive precipitation in December caused flooding in several places, including along the Missouri River. It is worth mentioning that not all places in the High Plains had above normal precipitation during December. Parts of Wyoming, eastern Colorado, northwestern Kansas, and southwestern Nebraska missed out and received 50 percent of normal precipitation, at best. One particularly dry area was Goodland, KS, which only received 0.16 inches (4 mm) of precipitation for the month, or 35 percent of normal. However, the month was nowhere near record-breaking compared to other Decembers on record. Luckily, at this time of year, deficits do not accumulate quickly, as even 50 percent of normal may only translate into a deficit of a half inch.
Snowpack is faring well in Colorado, thanks to ample snowfall during the latter half of December. According to the Natural Resources Conservation Service SNOTEL data, snow water equivalent was above 100 percent of median for most of the state as of the end of December, with the exception of a few SNOTEL sites in the northern part of the state. Snowpack is not faring as well in Wyoming, however. Dry conditions have led to below normal snowpack across the northern and central parts of the state, particularly in the Bighorn Mountains. Because it is early in the season, it is important to keep in mind that these conditions can change quite dramatically over the course of the season. There were both improvements and degradations in drought conditions across the High Plains region in December, according to the U.S. Drought Monitor. The two areas of moderate drought (D1) in central and eastern Kansas that were present at the beginning of the month were removed by mid-December due to excessively wet conditions. Parts of the areas that were previously in drought have received as much as 300 percent of normal precipitation since November. Above normal precipitation in December also improved drought conditions and abnormal dryness (D0) in the Dakotas, although a small area of D1 remains in southern North Dakota. Pockets of D0 were also removed from the Nebraska panhandle, southern Nebraska, and northern and central Colorado. Some parts of the region missed out on the excessive precipitation in December, leading to degradations in drought conditions. North-central Wyoming was placed into moderate drought (D1) in late December. This area received 50-70 percent of normal precipitation in December, at best. In fact, this region experienced below normal precipitation during the fall months as well. This particular region contains the Bighorn Mountains, and the snowpack season has not gotten off to a very good start there. The Climate Prediction Center's precipitation outlook for January is calling for a continuation of below normal precipitation in the area, so it is possible that drought conditions in northern Wyoming will expand and/or intensify over the next month.