May 2021 was the sixth-warmest May since global record-keeping began in 1880, 0.81 degrees Celsius (1.46°F) above the 20th-century average, NOAA’s National Centers for Environmental Information, NCEI, reported June 14. NASA rated the month the seventh warmest May on record. The relative coolness of May, by recent standards, was partially the result of a La Niña event in the Eastern Pacific that had dissipated earlier in the year: Its cool waters helped depress global surface temperatures.

January-May ranked as Earth’s eighth warmest such period on record, falling behind 2010 and also the six years of extreme warmth from 2015 to 2020. According to NCEI’s annual temperature outlook, the year 2021 is virtually certain to rank among the 10 warmest years on record, and more than 90% likely to fall in the range of sixth- to seventh-warmest on record. NCEI gives 2021 less than a 1% chance of becoming the warmest year on record, reflecting the modest cooling influence of the La Niña event in the Eastern Pacific early this year.

Figure 1. Departure of temperature from average for May 2021, the sixth-warmest May for the globe since record keeping began in 1880. Record-warm May temperatures were observed in parts of northern Africa, the Middle East, central Asia, and southeast China, as well as parts of the Southeast Pacific and Atlantic oceans. Record cold was observed in a small part of eastern India, due to the impact of Cyclone Yaas. (Image credit: NOAA/NCEI)

Global ocean temperatures during May 2021 were the 8th-warmest on record, and global land temperatures the 6th-warmest on record. No statistics were available for the global satellite-measured temperatures of the lowest eight kilometers of the atmosphere.

May 2021:  near-average for warmth, dryness in U.S.

The U.S. experienced near-average warmth in May. California had its ninth-warmest May on record; no other state had a top-10 warmest or coldest May. The year-to-date January-May period ranked in the top 23% for warmth, historically.

May 2021 precipitation over the contiguous U.S. was near-average, though California, Utah and Florida recorded a top-10 driest May, and  Texas and Louisiana a top-10 wettest May. According to the U.S. Drought Monitor, approximately 44% of the contiguous U.S. was in drought on May 25, making 2021 a tie with 2013 for the highest drought coverage in late May since the Drought Monitor was established in 2000.

The 12-month period ending May 2021 was the driest on record for California, Arizona, and Utah, second-driest for Nevada, and third-driest for New Mexico. The latest seasonal drought forecast from NOAA, issued May 20, calls for drought to expand and cover virtually all of the region west of the Rocky Mountains by the end of August. Drought conditions in the U.S. had already cost at least $1 billion by the end of May, according to insurance broker Aon.

Three billion-dollar weather disasters in May; 14 so far in 2021

Earth experienced effects of three billion-dollar weather disasters in May 2021, according to Aon: a severe weather and flash flooding episode in the U.S., and two cyclones in India, Tauktae and Yaas. Through the end of May, Earth had experienced 14 billion-dollar weather disasters, Aon reported, having tabulated a record 50 billion-dollar weather disasters during all of 2020. Below are the details on May’s disasters.

May billion-dollar weather disaster #1: An atmospheric river of moisture from the Gulf of Mexico brought severe weather and flash flooding across the U.S. Plains and Lower Mississippi Valley on May 14-19, killing five and costing $1.1 billion. Above: Louisiana State Fire Marshal personnel respond to flooding in the Lake Charles area on May 17, 2021. (Image credit: Louisiana State Fire Marshal)
May billion-dollar weather disaster #2: Tropical Cyclone Tauktae made landfall in western India’s Gujarat coast on the Arabian Sea on May 17 as a category 3 storm with 125 mph winds (1-minute average). This tied with the May 20, 1999 cyclone as the strongest landfalling Arabian Sea cyclone on record. At its peak intensity (0 UTC, May 17), Tauktae was a category 4 storm with 140 mph winds, making it the fifth-strongest tropical cyclone on record in the Arabian Sea, according to records of the Joint Typhoon Warning Center. Tauktae killed 198 people and did $1.5 billion in damage. Above:Visible satellite image of Cyclone Tauktae from the VIIRS instrument on the NOAA-20 satellite on May 17, 2021. (Image credit: NASA Earth Observatory)
May billion-dollar weather disaster #3: Tropical Cyclone Yaas made landfall in northeast India’s West Bengal state on May 26 as a category 1 storm with 75 mph winds, according to the Joint Typhoon Warning Center. Yaas killed 19 people and did $3 billion in damage; $2.7 billion of that total occurred in West Bengal. Above:People protect a dike with their bodies against Cyclone Yaas’ storm surge on May 26 along the Sundarbans coast of India. (Image credit: Association for India’s Development)

No El Niño or La Niña

Neutral conditions were in place during May, NOAA reported in its June 10 monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO.

Over the past month, sea surface temperatures in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W) were near average. The range for “weak” La Niña conditions is 0.5-1.0 degree Celsius below average.

Forecasters at NOAA and at Columbia University’s International Research Institute for Climate and Society say they expect La Niña conditions to remain “neutral” during the northern summer of June-July-August (78% chance). The forecast for the fall (September-October-November) is for a 43% chance of La Niña, 50% chance of ENSO-neutral, and a 7% chance of El Niño. Historically, about half of all winter La Niña events have continued into or re-emerged during the following winter.

Figure 2. Departure of sea surface temperature (SST) from average in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W). Temperatures were near average over the past month. (Image credit: Tropical Tidbits)

Arctic sea ice: ninth-lowest May extent on record

Arctic sea ice extent during May 2021 was the ninth-lowest in the 43-year satellite record, according to the National Snow and Ice Data Center. The relatively slow loss of ice during the month came about largely as the result of a series of storms that migrated over the North Pole.

Antarctic sea ice extent during May was near average.

Notable global heat and cold marks for May 2021

The information below is courtesy of Maximiliano Herrera. Follow him on Twitter: @extremetemps.

– Hottest temperature in the Northern Hemisphere: 50.1°C (122.2°F) at Sibi, Pakistan, May 30;
– Coldest temperature in the Northern Hemisphere: -43.0°C (-45.4°F) at Summit, Greenland, May 1;
– Hottest temperature in the Southern Hemisphere: 38.1°C (100.6°F) at Mandora, Australia, May 1;
– Coldest temperature in the Southern Hemisphere: -79.9°C (-111.8°F) at Vostok, Antarctica, May 20;
– Highest 2021 average temperature to date (Jan.-May) in the Southern Hemisphere: 30.0°C (86.0°F) at Marble Bar, Australia; and
– Highest 2021 average temperature to date (Jan.-May) in the Northern Hemisphere: 33.3°C (91.9°F) at Yelimane, Mali.

Major weather stations’ new all-time heat or cold records in May 2021

Among global stations with a record of at least 40 years, three set, not just tied, all-time heat records in May. No stations set all-time cold records:

– Yuanjiang (China) max. 44.1°C (111.4°F), May 23;

– Manila Airport (Philippines) max. 38.6°C (101.5°F), May 29; and

– Echague (Philippines) max. 41.6°C (106.9°F), May 30.

One all-time national/territorial cold record set or tied in 2021

As of May 31, 2021, one nation or territory had set or tied an all-time national cold record:

United Arab Emirates (for places at low elevations): -2.0°C (28.4°F) at Raknah, January 9.

No all-time national/territorial heat records have been set so far in 2021.

Forty-eight monthly national/territorial heat records beaten or tied as of May 31

– January (10): Mexico, Bangladesh, Nigeria, Japan, Malta, Tunisia, Turkey, Russia, Georgia, Spain
– February (12): Iraq, Uzbekistan, Mongolia, South Korea, Liechtenstein, Slovenia, Croatia, Slovakia, Poland, Sweden, Pakistan, Northern Mariana Islands
– March (14): Northern Mariana Islands, Qatar, Saudi Arabia, Bahrain, Kuwait, Pakistan, Oman, Jersey, Guernsey, Germany, Netherlands, Luxembourg, Belgium, US Virgin Islands
– April (4): South Africa, Northern Mariana Islands, Hong Kong, Tajikistan
– May (8): Northern Mariana Islands, Taiwan, Russia, Qatar, Turkmenistan, Uzbekistan, Dominica, Saba

Two monthly national/territorial cold records beaten or tied as of May 31

– April (2): Slovenia, Switzerland

Hemispherical and continental temperature records in 2021

– Highest minimum temperature ever recorded in April in the Southern Hemisphere: 31.7°C (89.1°F), at Vioolsdrif, South Africa, April 13.
– Highest minimum temperature ever recorded in May in Europe: 29.4°C (84.9°F), at Zymbragou, Greece, May 2.

Also see: April 2021: Ninth-warmest April on record, NOAA and NASA report.

Thanks to Bob Henson for contributing to this post.

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...