April 2021 was the ninth-warmest April since global record-keeping began in 1880, 0.79 degrees Celsius (1.42°F) above the 20th-century average, NOAA’s National Centers for Environmental Information, NCEI, reported May 13. NASA also rated the month as the ninth warmest April on record. In both NOAA and NASA data, April 2021 came in as the coolest April since 2013. The relative coolness of April was partially the result of a dissipating La Niña event in the Eastern Pacific: Its cool waters helped depress global surface temperatures. April 2021 was Europe’s coolest April since 2003, according to the European Copernicus Climate Change Service.

The year-to-date period January-April ranked as Earth’s eighth warmest such period on record, falling behind 2010 as well as 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 95% likely to fall in the range of fourth- to ninth-warmest on record. The NCEI outlook finds that 2021 has a less than 1% chance of becoming the warmest year on record, reflecting the modest cooling influence of the La Niña event in the Eastern Pacific at the beginning of 2021.

Figure 1
Figure 1. Departure of temperature from average for April 2021, the ninth-warmest April for the globe since record keeping began in 1880. Record-warm April temperatures were limited to parts of southern South America, southern Africa, and the Middle East, as well as small parts of the Pacific, Indian, and Atlantic oceans. No portion of the globe was record-cold. (Image credit: NOAA/NCEI)

Global ocean temperatures during April 2021 were the 8th-warmest on record, and global land temperatures were the 12th-warmest on record. Global satellite-measured temperatures in April 2021 for the lowest eight kilometers of the atmosphere were the 20th-warmest in the 43-year record, according to the University of Alabama in Huntsville.

April 2021:  above-average for warmth, dryness in U.S.

The U.S. experienced above-average warmth in April, with the month ranking in the top third for warmth since records began in 1895, according to NOAA. California, Arizona, and Maine experienced a top-10 warmest April. The year-to-date period January-April ranked in the top 22% for warmth, historically.

April 2021 precipitation over the contiguous U.S. was the 14th-lowest on record, with California, Oregon, Washington, and Idaho recording a top-10 driest April. According to the U.S. Drought Monitor, approximately 48% of the contiguous U.S. was in drought on May 8. This ties 2021 with 2013 for the highest drought coverage in early May since the Drought Monitor was established in 2000.

The 12-month period ending April 2021 was the driest on record for Nevada, Arizona, and New Mexico, and second-driest for California and Utah. The latest seasonal drought forecast from NOAA, issued April 15, calls for drought to creep eastward into the Plains and expand northward though most of the Pacific Northwest by the end of July. Drought conditions in the U.S. had already cost at least $1 billion by the end of April, according to insurance broker Aon.

Billion-dollar weather disasters of 2021

Four billion-dollar weather disasters in April; 11 so far in 2021

Four billion-dollar weather disasters affected Earth in April 2021, according to insurance broker Aon: a severe weather outbreak in the U.S., an April freeze in Europe that did heavy damage to agriculture, and droughts in the U.S. and in Mexico. Through the end of April, Earth had experienced 11 billion-dollar weather disasters, Aon reported. They tabulated a record 50 billion-dollar weather disasters during all of 2020. Below are the details on April’s disasters.

Billion-dollar disaster 1
April billion-dollar weather disaster #1: Record-breaking warmth affected much of Europe in late March, promoting an early bud-out and flowering of plants. Jersey, Guernsey, Germany, Netherlands, Luxembourg, and Belgium all set records for hottest temperature ever measured in March. Unfortunately, the warm spell was followed by record-breaking cold during the first half of April. Numerous locations had record April lows, and freezing temperatures caused significant damage to flowering fruit trees, viticulture and other vegetation. Damage was estimated at over $5 billion, with France alone suffering $2.4 billion in damage. Damage was also heavy in Italy. Above: Smoke rises from fires lit to prevent freeze damage in a French vineyard on April 8, 2021. (Image credit: Christiane Lambert, FNSEA)
Billion-dollar disaster 2
April billion-dollar weather disaster #2: A severe weather outbreak across the Plains on April 27-30 featured damaging tornadoes, strong straight-line winds, and large hail. Total damage was estimated at $1 billion, but there were no fatalities. Most of the damage was due to major hail storms on April 28 that affected San Antonio, TX; Fort Worth, TX; and Norman, OK. Above: Infrared satellite image of supercell thunderstorms over Texas and Oklahoma near sunset on April 28. (Image credit: NOAA)
Billion-dollar disaster 3
April billion-dollar weather disaster #3: One of the most widespread and intense droughts in western U.S. history had already caused at least $1 billion in damages by the end of April, Aon estimated. Above: California’s largest reservoir, Lake Oroville, as seen on April 26, 2021. (Image credit: California DWR)
Billion-dollar disaster 4
April billion-dollar weather disaster #4: According to NASA, “Mexico is experiencing one of its most widespread and intense droughts in decades. Nearly 85 percent of the country is facing drought conditions as of April 15, 2021. Large reservoirs across the country are standing at exceptionally low levels, straining water resources for drinking, farming, and irrigation. The mayor of Mexico City called it the worst drought in 30 years for the city, which is home to about 9 million people.” By the end of April, Aon estimated the year-to-date costs of Mexico’s drought at $1 billion. Above: where vegetation is stressed due to lack of water, estimated using the Evaporative Stress Index (ESI) index. (Image credit: NASA Earth Observatory)

Deadliest weather disaster of 2021: Cyclone Seroja

The deadliest weather disaster so far in 2021 has been Cyclone Seroja, which triggered flash flooding and massive landslides as it wandered slowly over southeastern Indonesia and Timor-Leste as a tropical depression and tropical storm on April 3-5, before making landfall in West Australia as a category 1 storm on April 11. Seroja killed 230 in Indonesia, 42 in Timor-Leste, and one in Australia. Total damage was estimated at $625 million; $240 million of the total occurred in Indonesia’s East Nusa Tenggara province.

Seroja’s total death toll of 273 makes it the fourth-deadliest tropical cyclone on record in the Australian region. (Thanks go to the Australian Bureau of Meteorology’s Jeff Callaghan for helping assemble the list below.)

Deadliest tropical cyclones of the Australian region
Figure 2. Top-ten deadliest tropical cyclones in the Australian region. Background image: Flood damage from Cyclone Seroja in Flores, Timor on April 4, 2021. (Image credit: Indonesia BPBD)

La Niña ends

The moderate La Niña event that began in the summer of 2020 ended in April 2021, said NOAA in its May 13 monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO. The Australian Bureau of Meteorology, which uses a more stringent threshold than NOAA for defining La Niña, reported that the 2020-2021 La Niña event ended in March.

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) have averaged about 0.1 degrees Celsius below average, falling in the “neutral” range. The range for “weak” La Niña conditions is 0.5-1.0 degrees Celsius below average.

Forecasters at NOAA and at Columbia University’s International Research Institute for Climate and Society expect La Niña conditions to remain “neutral” during the northern summer of June-July-August (67% chance). The forecast for the fall (September-October-November) is for a 49% chance of La Niña, 43% chance of ENSO-neutral, and an 8% chance of El Niño, with the odds of La Niña rising above 50% from late autumn into winter. Historically, about half of all La Niña events have continued into or re-emerged during a second year.

Figure 3
Figure 3. 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). SSTs ranged from 0-0.3°C below average over the past month, and did not reach the 0.5 degrees Celsius below-average threshold for weak La Niña conditions. (Image credit: Tropical Tidbits)

Arctic sea ice: sixth-lowest April extent on record

Arctic sea ice extent during April 2021 was the sixth-lowest in the 43-year satellite record, remaining below the tenth percentile range throughout April, according to the National Snow and Ice Data Center. There was little change in the age distribution of the ice compared to last year; at the end of the ice growth season in mid-March, 73.3% of the Arctic Ocean domain was covered by first-year ice, while 3.5% was covered by ice 4+ years old. In March 1985, near the beginning of the ice age record, there was nearly equal amounts of first-year ice (39%) and 4+ year-old ice (30.6%).

Antarctic sea ice extent during April was above average during the beginning of the month, and close to average by the end of the month.

Notable global heat and cold marks for April 2021

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

– Hottest temperature in the Northern Hemisphere: 47.0°C (116.6°F) at Matam, Senegal, April 12;
– Coldest temperature in the Northern Hemisphere: -57.8°C (-72.0°F) at Summit, Greenland, April 4;
– Hottest temperature in the Southern Hemisphere: 44.8°C (112.6°F) at Violsdrif, South Africa, April 13;
– Coldest temperature in the Southern Hemisphere: -75.8°C (-104.4°F) at Dome Fuji, Antarctica, April 20;
– Highest 2021 average temperature to date (Jan.-Apr.) in the Southern Hemisphere: 31.0°C (87.8°F) at Marble Bar, Australia; and
– Highest 2021 average temperature to date (Jan.-Apr.) in the Northern Hemisphere: 32.5°C (90.5°F) at Kenieba, Mali.

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

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

– Putao (Myanmar) max. 39.0°C (102.2°F), April 24.

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

As of April 30, 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 thus far in 2021.

Forty monthly national/territorial heat records beaten or tied as of April 30

– 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

Two monthly national/territorial cold records beaten or tied as of April 30

– 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.

Also see: March 2021 was eighth-warmest March on record, NOAA reports

Thanks to Bob Henson for contributing to this post.

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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...