May 2018 Global Climate Report

May 2018 Selected Climate
Anomalies and Events Map

Introduction

Temperature anomalies and percentiles are shown on the gridded maps below. The anomaly map on the left is a product of a merged land surface temperature (Global Historical Climatology Network, GHCN) and sea surface temperature (ERSST.v4) anomaly analysis as described in Huang et al. (2016). Temperature anomalies for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCEI's Global Surface Temperature Anomalies page. The percentile map on the right provides additional information by placing the temperature anomaly observed for a specific place and time period into historical perspective, showing how the most current month, season or year compares with the past.

Temperatures

In the atmosphere, 500-millibar height pressure anomalies correlate well with temperatures at the Earth's surface. The average position of the upper-level ridges of high pressure and troughs of low pressure—depicted by positive and negative 500-millibar height anomalies on the May 2018 and March–May 2018 maps—is generally reflected by areas of positive and negative temperature anomalies at the surface, respectively.

May

May 2018 Blended Land and Sea Surface
Temperature Anomalies in degrees Celsius

May 2018 Blended Land and Sea Surface
Temperature Percentiles

Warmer-than-average conditions engulfed much of the world's land and ocean surfaces, giving way to the fourth highest May temperature since global records began in 1880. The May 2018 combined average temperature over the global land and ocean surfaces was 0.80°C (1.44°F) above the 20th century average of 14.8°C (58.6°F). The years 2014–2018 rank among the five warmest Mays on record, with 2016 the warmest May at +0.88°C (+1.58°F). May 2018 also marks the 42nd consecutive May and the 401th consecutive month with temperatures, at least nominally, above the 20th century average. The most notable warm temperature departures from average during May 2018 were present across much of the contiguous U.S. and Europe, where temperatures were 3.0°C (5.4°F) above average or higher. In contrast, the most notable cool temperature departures from average were present across northeastern Canada and central Russia where temperatures were 3.0°C (5.4°F) below average or lower. Record warmth was observed across parts of North America, Europe, Asia, as well as the Atlantic, Pacific, and Indian Oceans. Record cold May temperatures were limited to northeastern Canada and the northern Atlantic Ocean, off the southern coast of Greenland. According to NCEI's Regional Analysis, four of the six continents had a May temperature that ranked among the nine highest on record, with Europe and North America having their highest and second highest May temperature on record, respectively. Also of note, Asia's rank of 15th warmest for May 2018 was the smallest May temperature departure from average since 2009.

The global land surface temperature for May 2018 was the coolest May since 2011 and tied with 2013 as the seventh highest in the 139-year record at 1.14°C (2.05°F) above the 20th century average of 11.1°C (52.0°F). The global oceans had their smallest temperature departure for May since 2014 and was also the fourth highest May temperature on record at 0.66°C (1.19°F) above the 20th century average of 16.3°C (61.3°F).

Select national information is highlighted below. Please note that different countries report anomalies with respect to different base periods. The information provided here is based directly upon these data:

• Much of North America had warmer-than-average conditions during May 2018. According to NCEI's Regional Analysis, May 2018 temperature North America was 1.74°C (3.13°F) above average—the second highest May temperature, behind the record year 1998 (+1.94°C / +3.49°F).
• The contiguous U.S. May 2018 temperature was 2.89°C (5.2°F) above the 20th century average and the highest May temperature since national records began in 1895. This value exceeds the previous record set in 1934 by +0.4°C (+0.7°F). Eight states had record warm May temperatures.
• Near- to cooler-than-average May temperatures engulfed much of Alaska during May 2018, resulting in its coolest May temperature since 2013 and the 38th warmest May since statewide records began in 1925.
• During May 2018, the southern half of Canada had much-warmer-than-average conditions, while the northern half had near- to much-cooler-than-average conditions.
• Europe had its warmest May since continental records began in 1910 at +2.76°C (4.97°F), surpassing the previous record set in 2003 by +0.92°C (+1.66°F). May 2018 marks the first time in May that the continental temperature departure from average is 2.0°C (3.6°F) or higher. May 2018 was the 11th highest monthly temperature departure among all 1,313 months on record. The highest monthly temperature departure for Europe is February 1990 at +3.91°C (+7.04°F).
• The United Kingdom had its second warmest May (tied with 2017) since national records began in 1910. The May 2018 temperature of 12.1°C (53.8°F) was 1.7°C (3.1°F) above the 1981–2010 average. Provisionally, England and Scotland had their highest May temperature (England: tied with 1992 and 2008; Scotland: tied with 2008) in the 109-year record.
• Warmer-than-average conditions were present across much of Sweden during May 2018, with several locations experiencing their warmest May on record. Stockholm, Sweden set a new maximum May temperature of 16.1°C (61.0°F), which is 2.2°C (4.0°F) greater than the previous record set in 1993. Stockholm's data records began in 1756. On May 30th, the maximum temperature soared to 31.1°C (88.0°F) in Göteborg—this was the highest daily maximum temperature in Sweden since 1911 when Nora in Västmanland had 31.3°C (88.3°F).
• Warmer-than-average conditions engulfed much of Norway during May 2018, with a national average temperature that was 4.4°C (7.9°F) above average and the warmest May since national records began in 1900. The previous record was set in 2013 (+2.7°C / +4.9°F). According to Meteorologisk Institutt, several stations across southern Norway had temperatures that were 5.0°C–7.0°C (9.0°F–12.6°F) above average. Of note, Blindern, Oslo, had a monthly temperature of 16.1°C (61.0°F) or 5.3°C (9.5°F) above average, Norway's highest May temperature on record.
• According to Meteorologisk Institutt, five Arctic stations (Bjørnøya, Hopen, Svalbard airport, Ny-Ålesund, and Jan Mayen) had a record warm May. Of note, the Svalbard airport May 2018 average temperature was 1.8°C (35.2°F), which is 6.0°C (10.8°F) above average and marks the 90th consecutive month with temperatures above average.
• May 2018 marked the second consecutive month that Germany's monthly national average temperature set a new temperature record. Germany's May 2018 temperature of 16.0°C (60.8°F) was 3.9°C (7.0°F) above the 1961–1990 average—the highest May temperature since national records began in 1881. This value was also 0.6°C (1.1°F) warmer than the June 1961–1990 average.
• Finland had its warmest May on record at 11.6°C (52.9°F), surpassing the previous record set in 1963 by +0.5°C (+0.9°F). Several stations across Finland observed their warmest May on record. Of interest, Kumpula, Helsinki, had an average May temperature of 15.5°C (59.9°F), setting a new Finnish record. This value exceeded the previous record set in 2016 at the Helsinki Airport by +1.2°C (+2.2°F). According to the Finnish Meteorological Institute, May has an average of three hot days (maximum temperature > 25.0°C (77.0°F)). However, May 2018 had a total of 14 hot days, resulting in Finland's highest number of hot days for May. The previous record was 12 hot days set in 1984.
• Denmark's May 2018 mean temperature of 15.0°C (59.0°F) was 4.2°C (7.6°F) above the 1961–1990 average—this was the highest May temperature since national records began in 1874. This value was 1.2°C (2.2°F) higher than the previous record set in 1889. The nation's maximum and minimum temperatures were also warmer than average, ranking as the highest (20.5°C / 68.9°F) and second highest (9.1°C / 16.4°F) since 1953, respectively. The May 2018 maximum temperature surpassed the previous record set in 1993 by +2.8°C (+5.0°F). The May 2018 minimum temperature was only 0.2°C (0.4°F) shy of tying the record set in 2002. Copenhagen, Denmark's capital, set a new May maximum temperature record on May 30 when temperatures soared to 29.3°C (84.7°F), exceeding the previous record of 28.5°C (83.3°F) set in 1886.
• Austria had its warmest May since 1868 and the fourth warmest since national records began in 1767, falling behind 1811, 1868, and 1797. Austria's national May 2018 temperature was 2.6°C (4.7°F) above average.
• Argentina's national mean temperature for May 2018 was 1.3°C (2.3°F) above average and the seventh highest since national records began in 1961. Several regions in northern Argentina (Misiones, Salta and Jujuy) had a May temperature that ranked among the five highest Mays on record. Several locations set a new maximum temperature record for the month of May. Of note, Presidencia Roque Saenz Peña set a new maximum temperature of 36.6°C (97.9°F) on May 3.
• Australia's mean temperature for May 2018 was 0.19°C (0.34°F) above the 1961–1990 average and was the 44th warmest May since national records began in 1910. The nation's above-average mean temperature was mainly driven by the warmer-than-average maximum temperature (+0.86°C / +1.55°F), which ranked as the 26th warmest May maximum temperature on record. The largest warm maximum temperature departure from average was observed in New South Wales (+1.31°C / +2.36°F). Meanwhile, the national minimum temperature was -0.49°C (-0.88°F) and the 43rd coldest May in the 109-year record.
• A cold front brought cooler-than-average conditions to southeastern Australia on May 10. Melbourne's maximum temperature that day was 12.8°C (55.0°F)—the city's coldest day so early in the season since 1970.
• New Zealand's May 2018 temperature was 11.2°C (52.2°F) or 0.4°C (0.7°F) above the 1981–2010 average. Several locations had near-record mean, maximum, and minimum temperatures during May 2018. Of interest, Culverden and Akaroa (both town's located in the South Island) had a minimum temperature departure of +3.1°C (+5.6°F), the third highest May minimum temperature for both of these locations.

ENSO-neutral conditions persisted across the tropical Pacific Ocean during May 2018. According to NOAA's Climate Prediction Center, ENSO-neutral conditions are favored through the Northern Hemisphere summer (Southern Hemisphere winter) 2018. This forecast focuses on the ocean surface temperatures between 5°N and 5°S latitude and 170°W to 120°W longitude, called the Niño 3.4 region.

May Global Land and Ocean plot

May Global Hemisphere plot

The most current data can be accessed via the Global Surface Temperature Anomalies page.

Seasonal (March–May)

March–May 2018 Blended Land and Sea Surface
Temperature Anomalies in degrees Celsius

March–May 2018 Blended Land and Sea Surface
Temperature Percentiles

The period of March–May is defined as the Northern Hemisphere's spring and the Southern Hemisphere's autumn.

Warmer-than-average conditions were present across much of the global land and ocean surfaces during March–May. Record warm temperatures during the three-month period were present across parts of southern Europe, the Middle East, northeastern Africa, China, Mongolia, and scattered across the South America, Atlantic, Indian, and Pacific Oceans. Cooler-than-average conditions were present across western Russia, north Atlantic (off the southern coast of Greenland), central Indian Ocean, and the eastern and central tropical Pacific Ocean. No land or ocean areas had record cold temperatures during March–May 2018. According to NCEI's Regional Analysis, five of the six continents had a March–May temperature that ranked among the nine warmest such periods on record, with Europe and South America having their third warmest such period on record.

The global land and ocean surface temperature for March–May 2018 was 0.82°C (1.48°F) above the 20th century average of 13.7°C (56.7°F) and the fourth warmest such period in the 139-year records, trailing behind 2016 (+1.07°C / +1.93°F), 2017 (+0.91°C / +1.64°F), and 2015 (+0.85°C / +1.53°F). Globally, the average land surface temperature was the fifth highest March–May on record at 1.30°C (2.34°F) above the 20th century average of 8.1°C (46.4°F). The global ocean temperature was 0.64°C (1.15°F) above the 20th century average of 16.1°C (61.0°F) and was also the fourth highest on record.

Select national information is highlighted below. (Please note that different countries report anomalies with respect to different base periods. The information provided here is based directly upon these data):

• For Australia, as a whole, March–May 2018 ranked as the fourth highest mean temperature since national temperature records began in 1910 at +1.18°C (+2.12°F). Regionally, New South Wales, Victoria, South Australia, and Western Australia had a top eight warm March–May, with New South Wales having its second highest autumn temperature on record (+1.88°C / +3.38°F). This value is 0.33°C (0.59°F) lower than the record set in 2016. The national maximum temperature was also the fourth highest on record at +1.74°C (+3.13°F). New South Wales had its highest maximum March–May temperature on record (+2.66°C / +4.79°F), surpassing the previous record of +2.41°C (+4.34°F) set in 2016.
• Austria's spring 2018 temperature was 2.0°C (3.6°F) above average—the second warmest such period since national records began in 1767, trailing behind 2007 by 0.1°C (0.2°F). Several stations across Austria set new records for the most number of summer days (maximum temperature ≥ 25.0°C (77.0°F)) observed during the March–May period. Of note, Vienna Hohe Warte had a total of 24 summer days during spring 2018, exceeding the previous record set in 1969 (18 summer days).

March–May Global Land and Ocean plot

March–May Global Hemisphere plot

Year-to-date (January–May)

January–May 2018 Blended Land and Sea Surface
Temperature Anomalies in degrees Celsius

January–May 2018 Blended Land and Sea Surface
Temperature Percentiles

The first five months of the year were characterized by warmer-than-average temperatures engulfing much of the globe's land and ocean surfaces. Record warm January–May temperatures were observed scattered across South America, southeastern Europe, northeastern Africa, Asia, New Zealand, Australia, and Mexico, as well as across all oceans. Averaged as a whole, the January–May 2018 temperature over the land and ocean surfaces tied with 2010 as the fourth warmest such period in the 139-year record, with an average temperature that was 0.77°C (1.39°F) above the 20th century average of 13.1°C (55.5°F). This value is the smallest January–May temperature departure from average since 2014.

The global land surface temperature during January–May 2018 was 1.21° (2.18°F) above the 20th century average of 6.0°C (42.8°F)—tying with 2002 as the fifth highest such period since global records began in 1880. According to NCEI's Regional Analysis, five of six continents had a January–May temperature that ranked among the eight warmest such periods on record, with Oceania having its second warmest such period on record. Across the oceans, the January–May 2018 global oceans temperature was 0.60°C (1.08°F) above the 20th century average of 16.0°C (60.8°F) and the fifth warmest such period on record.

January–May Global Land and Ocean plot

January–May Global Hemisphere plot

Precipitation

May

The maps below represent precipitation percent of normal (left, using a base period of 1961–1990) and precipitation percentiles (right, using the period of record) based on the GHCN dataset of land surface stations. As is typical, precipitation anomalies during May 2018 varied significantly around the world. May precipitation was generally drier than normal across the western half of the contiguous U.S., northern Mexico, eastern Brazil, southern Chile, Portugal, southern Spain, as well as northern and eastern Europe, Mongolia, northern India, southern Africa, and Australia. Wetter-than-normal conditions were notable across the eastern half of the contiguous U.S., southern South America, central and southeastern Europe, Turkey, northwestern Africa, southern India, central Russia, South Korea, and Japan.

Select national information is highlighted below. (Please note that different countries report anomalies with respect to different base periods. The information provided here is based directly upon these data):

• Drier-than-average conditions plagued much of Australia during May 2018, resulting in the driest May since 2008 and the third driest May since national precipitation records began in 1900 at 8.7 mm (0.3 inch) or 69% below average. Regionally, New South Wales had its driest May since 2006 and the seventh lowest in the 119-year record. Several stations across New South Wales had record low or their lowest May precipitation totals for at least 20 years. In contrast, Tasmania was the only region that had near-average May precipitation. A cold front impacted the region on May 10, resulting in several daily record precipitation totals in parts of southeastern Tasmania.
• Wetter-than-average conditions were present across the northern half of Argentina. Córdoba and Santa Fe provinces had their wettest May on record, with several other provinces having near-record May precipitation. Averaged as a whole, Argentina had its wettest May since national records began in 1961.
• Drier-than-average conditions affected much of Sweden during May 2018. Several locations had record or near-record dry conditions. Visby, Gotland, had its driest May since records began in 1859, with a precipitation total of 1.7 mm (0.07 inch) for May 2018. This value is 1.1 mm (0.04 inch) less than the previous record set in 1866. Also of note, Öland's Northern Cape had 0.2 mm (0.01 inch) and the driest May since 1947.
• Cyclone Mekunu, the tenth tropical cyclone in the Arabian Sea in the last 11 years, ranked as the fourth strongest cyclone over the Arabian Sea. It was reported that Salalah, Oman, had a total of 328 mm (12.9 inches) in a 36-hour period from May 24–25— this is over twice the annual average precipitation of 130 mm (5.1 inches) for the city.

May 2018 Land-Only Precipitation
Percent of Normal

May 2018 Land-Only Precipitation Percentiles

Seasonal (March–May)

As is typical, precipitation anomalies during March–May 2018 varied significantly around the world. During March–May 2018, above-average seasonal precipitation was observed across the eastern and northwestern contiguous U.S., western Europe, South Korea, Japan, some western Pacific Islands, and parts of northeastern Brazil and northeastern Argentina. Drier-than-average conditions were notable across the central and western contiguous U.S., southern South America, eastern Europe, southern Asia, and Australia.

• Spring 2018 was drier-than-average across much of Austria, with some locations experiencing their driest spring since 2003.
• Australia, as a whole, had a drier-than-average autumn at 33% below the 1961–1990 average. This was the 20th driest March–May in the nation's 119-year record. Regionally, Western Australia had its driest such period since 1994 and the seventh driest autumn on record. New South Wales had its driest autumn since 2005 and the eighth driest on record.
• Heavy rain affected Kenya during March–May 2018. Some locations, such as Narok, Eldoret-Kapsoya, and Makindu, had their highest March–May precipitation totals in the last 50 years.

March – May 2018 Land-Only Precipitation
Percent of Normal

March – May 2018 Land-Only Precipitation Percentiles

References

• Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.
• Huang, B., V.F. Banzon, E. Freeman, J. Lawrimore, W. Liu, T.C. Peterson, T.M. Smith, P.W. Thorne, S.D. Woodruff, and H-M. Zhang, 2016: Extended Reconstructed Sea Surface Temperature Version 4 (ERSST.v4). Part I: Upgrades and Intercomparisons. J. Climate, 28, 911-930.

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