May 2024 was Earth’s warmest May since global record-keeping began in 1850 and was the planet’s 12th consecutive warmest month on record, NOAA’s National Centers for Environmental Information, or NCEI, reported June 13. Record heat was unusually widespread, with 16.1% of the world’s surface experiencing record heat, a record for the month of May.

NASA placed May at 1.37 degrees Celsius (2.47 °F) above the 1880-1899 period, its best estimate for when preindustrial temperatures last occurred. This beat the previous May record (from 2020) by an impressive 0.13 degrees Celsius (0.23 °F).

The European Copernicus Climate Change Service also rated May 2024 as the warmest May on record and said that the global average temperature for the past 12 months (June 2023-May 2024) was the highest on record for any 12-month period, 1.63 degrees Celsius above the 1850-1900 preindustrial average. 

Land areas had their warmest May on record in 2024, according to NOAA, and for the 14th consecutive month, global ocean temperatures were the warmest on record. The recent record heat in the oceans has brought on a global coral bleaching event, the fourth one in recorded history (1998, 2010, 2014-17, and now 2024).

It was the warmest May on record for Africa, third-warmest for Europe, fifth-warmest for North America, 11th-warmest for South America, ninth-warmest for Asia, and sixth-warmest for Oceania. The Caribbean Islands region had its warmest May on record, a remarkable 0.63 degrees Celsius (1.13°F) warmer than the previous record warm Mays of 2016 and 2020. The Main Development Region for hurricanes in the Atlantic also had its warmest May on record, 0.37 degrees Celsius (0.67°F) warmer than the previous record warm May of 2010.

The contiguous U.S. posted its 13th-warmest May, with much of the region bordering the Gulf of Mexico experiencing their hottest May on record. The tally of U.S. billion-dollar weather disasters so far in 2024 has been 11. The annual average for the most recent five years (2019–2023) is 20.4; the record was 28, set in 2023.

Satellite-measured temperatures of the planet’s lower atmosphere in May were the warmest on record for the month.

The January to May global surface temperature ranked warmest in NOAA’s 175-year record. According to NOAA/NCEI’s statistical analysis, there is a 50% chance that 2024 will rank as the warmest year on record and a 100% chance that it will rank in the top five. Climate scientist Zeke Hausfather gives a 75% chance that 2024 will beat 2023 as the warmest year on record; climate scientist Gavin Schmidt put these odds at 60%. The outcome will hinge largely on how quickly an evolving La Niña event works to bring down global temperatures from their current record-smashing pace during the second half of 2024.

Highest 2-year increase in CO₂ on record: 5.9 ppm

The global average concentration of carbon dioxide (CO2) in May 2024 was 5.9 parts per million (ppm) higher than in May 2022. This is the highest two-year increase in CO₂ levels ever recorded, NOAA announced on June 6. The surge has come even though the burning of fossil fuel, the main driver of climate change, has plateaued in recent years. The record two-year increase in CO2 from 2022 to 2024 is “likely a result of sustained high fossil fuel emissions combined with El Niño conditions limiting the ability of global land ecosystems to absorb atmospheric CO₂,” said John Miller, a carbon cycle scientist with NOAA’s Global Monitoring Laboratory.

Three very deadly weather disasters in May: floods in Brazil, East Africa, and Southwest Asia

Three highly deadly weather disasters occurred in May:

• Exceptionally heavy rains during late April and early May led to destructive floods in Brazil’s southern state of Rio Grande do Sul that killed at least 149 people and caused damages of over $1.7 billion, according to Aon. These rains were made twice as likely due to climate change, according to rapid study by an international team of leading climate scientists from the World Weather Attribution group.

• Heavy rains during the March-May portion of the annual spring rainy season in East Africa triggered floods that have left at least 559 people dead or missing, according to Aon. The death toll is the highest in Kenya, with 289 dead as of May 16. The flood death toll is 155 in Tanzania, 49 in Uganda, and 29 in Burundi. These heavy rains were made about twice as likely and 5% more intense because of human-caused climate change, according to the World Weather Attribution group. However, poor urban planning is at the heart of increasingly severe East African flood impacts in recent years, they said.

• Heavy downpours in Afghanistan, Iran and Pakistan in April and May led to flash floods that killed more than 400 people, destroyed homes, and wiped out crops.  The World Weather Attribution group found that that El Niño made the rainfall twice as likely, and limited coverage of early warning systems and the location of many homes in flood-prone areas turned the floods into incredibly deadly events. The increased rainfall could not formally attributed to climate change, but warming driven by the burning of fossil fuels was the most probable explanation for the heavier rainfall.

As discussed in our January post, Africa has suffered an unprecedented number of deadly weather-related disasters over the past two years; an astonishing seven of the continent’s 30 deadliest weather-related disasters since 1900 have occurred in 2022-23; all of these disasters killed over 500 people, with climate change found to be a contributing factor in four of the ones from 2021-2023. The 2024 floods give Africa eight of its top 30 deadliest weather disasters in the past three years.

El Niño ends; La Niña expected by late summer

The 2023-24 El Niño event in the Eastern Pacific ended during May, and neutral conditions are now in place, NOAA reported in its June monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO. There is a 65% chance of La Niña conditions developing by July-August-September, with an 85% chance of La Niña conditions during November-December-January.

For the climatological peak of the upcoming Atlantic hurricane season (August-September-October), the June forecast from NOAA and Columbia University’s International Research Institute for Climate and Society calls for a 75% chance of La Niña, a 24% chance of ENSO-neutral, and a mere 1% chance of El Niño. El Niño conditions tend to suppress Atlantic hurricane activity through an increase in wind shear, but La Niña conditions tend to have the opposite effect.

Arctic sea ice: 12th-lowest May extent on record

Arctic sea ice extent during May 2024 was the 12th-lowest in the 46-year satellite record, according to the National Snow and Ice Data Center, or NSIDC. The Arctic had its 11th-warmest May on record. Antarctic sea ice extent in May was the fifth-lowest on record, but was the second-lowest on record during the first week of June. The Antarctic region had its 23rd warmest May.

Notable global heat and cold marks for May 2024

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

• Hottest temperature in the Northern Hemisphere: 52.5°C (126.5°F) at Moen Jo Daro, Pakistan, May 26;
• Coldest temperature in the Northern Hemisphere: -43.4°C (-46.1°F) at Summit, Greenland, May 10;
• Hottest temperature in the Southern Hemisphere: 41.3°C (106.3°F) at Uitenhage, South Africa, May 3; and
• Coldest temperature in the Southern Hemisphere: -78.3°C (-108.9°F) at Concordia, Antarctica, May 9.

Major weather stations in May: 60 all-time heat records, no all-time cold records

Among global stations with a record of at least 40 years, 60 set, not just tied, an all-time heat record in May; no stations set an all-time cold record:

Tha Ngon (Laos) max. 43.7°C, May 1: New national record high for Laos;
Houei Sai (Laos) max. 42.1°C, May 1;
Danang (Vietnam) max. 41.5°C, May 1;
Anuradhapura (Sri Lanka) max. 39.8°C, May 1;
Chumphon (Thailand) max. 39.8°C, May 1;
Sawi (Thailand) max. 40.2°C, May 1;
Navrongo (Ghana) max. 44.6°C, May 1: New national record high in Ghana;
Loei (Thailand) max. 43.8°C, May 2;
Nandyal (India) max. 46.3°C, May 3;
Cuddapah (India) max. 46.2°C, May 3;
Kurnool (India) max. 45.9°C, May 3;
Tulancingo (Mexico) max. 35.5°C, May 7;
Managua (Nicaragua) max. 38.8°C, May 7;
Quetzaltenango (Guatemala) max. 30.2°C, May 7;
Orizaba (Mexico) max. 38.8°C, May 8;
San Cristobal de las Casas (Mexico) max. 31.7°C, May 8;
Rio Verde (Mexico) max. 45.2°C, May 9;
Campeche (Mexico) max. 45.1°C, May 9;
Progreso (Mexico) max. 44.2°C, May 9;
Queretaro (Mexico) max. 38.2°C, May 9;
Toluca (Mexico) max. 33.6°C, May 9;
Huajuapan de Leon (Mexico) max. 40.8°C, May 10;
San Luis Potosi (Mexico) max. 39.8°C, May 16;
Kyaukse (Myanmar) max. 44.2°C, May 16;
Santa Lucia (Cuba) max. 38.8°C, May 16;
Velasco (Cuba) max. 39.2°C, May 17;
Villahermosa (Mexico) max. 44.0°C, May 17;
Merida (Mexico) max. 44.2°C, May 17;
Flores (Guatemala) max. 43.8°C, May 17;
Puerto Barrios (Guatemala) max. 41.0°C, May 17;
Pachuca (Mexico) max. 34.5°C, May 17;
La Fragua (Guatemala) max. 44.8°C, May 18;
Santo Domingo (Cuba) max. 39.1°C, May 18;
Santiago de las Vegas (Cuba) max. 37.6°C, May 18;
Sombrerete (Mexico) max. 39.4°C, May 20;
Guanajuato (Mexico) max. 39.4°C, May 21;
Morelia (Mexico) max. 39.3°C, May 24;
Monclova (Mexico) max. 47.0°C, May 24;
Melena del Sur (Cuba) max. 37.2°C, May 25;
Dibrugarh (India) max. 38.8°C, May 25;
Silchar (India) max. 40.0°C, May 25;
Itanagar (India) max. 40.5°C, May 25;
Cooch Behar (India) max. 40.5°C, May 25;
Lumding (India) max. 43.0°C, May 25;
Pasighat (India) max. 39.6°C, May 25;
Aguascalientes (Mexico) max. 40.0°C, May 25;
Mexico City (Mexico) max. 34.7°C, May 25;
Pilani (India) max. 49.0°C, May 28;
Jhansi (India) max. 49.0°C, May 28;
Rewa (India) max.48.2°C, May 28;
Narnaul (India) max. 48.5°C, May 28;
Rohtak (India) max. 48.8°C, May 29;
Chandigarh (India) max. 46.0°C, May 29;
Una (India) max. 46.0°C, May 29;
Aguada de Pasajeros (Cuba) max. 38.3°C, May 29;
Paso Real de San Diego (Cuba) max. 38.2°C, May 29;
Pinar del Rio (Cuba) max. 37.8°C, May 29;
Sidhi (India) max. 49.2°C, May 30;
Butuan (Philippines) max. 38.0°C, May 31; and
Ciego de Avila (Cuba) max. 38.2°C, May 31.

Thirteen all-time national/territorial heat records beaten or tied as of the end of May

Cocos Islands (Australia): 32.8°C (91.0°F), Feb. 28, Feb. 29, Apr. 7 (tie);
Costa Rica: 41.0°C (105.8°F) at Cerro Huacalito, Mar. 6; broken again with 41.5°C, Mar. 23, at the same location;
Comoros: 36.2°C (97.2°F) at Hahaya Airport, Mar. 12;
Congo Brazzaville: 39.6°C (103.3°F) at Impfondo, Mar. 13;
Maldives: 35.1°C (95.2°F) at Hanimadhoo, Mar. 24; tied at the same location on Apr. 11;
Togo: 44.0°C (111.2°F) at Mango, Mar. 31;
Mali: 48.5°C (119.3°F) at Kayes, Apr. 3;
Belize: 42.3°C (108.1°F) at Barton Creek, Apr. 10; tied on May 17 at Chaa Creek;
Chad: 48.0°C (118.4°F) at Faya, Apr. 24 (tie);
Cambodia: 42.8°C (109.0°F) at Preah Viehar and Svay Leu, Apr. 27;
Laos: 43.7°C (110.7°F) at Tha Ngon, May 1; (3^rd time that the previous all-time record was beaten in 2024);
Ghana: 44.6°C (112.3°F) at Navrongo, May 1; and
Palau: 35.0°C (95.0°F) at Babelthuap Int. Airport, May 29 (tie).

One hundred five additional monthly national/territorial heat records beaten or tied as of the end of May

In addition to the 13 all-time national/territorial records set so far in 2024, 105 nations or territories have set or tied monthly all-time heat records as of the end of May 2024, for a total of 118 such records:

• Jan. (15): Mayotte, Dominica, Saba, Cocos Islands, Malta, Hong Kong, Ivory Coast, Maldives, Andorra, Portugal, Costa Rica, UK, Seychelles, Martinique, St. Barthelemy
• Feb. (18): Maldives, French Guiana, Guyana, Dominica, Curacao, St. Kitts and Nevis, Antigua and Barbuda, U.S. Virgin Islands, Belize, North Korea, Morocco, French Southern Territories, Hong Kong, Taiwan, Peru, Laos, Chad, Togo
• Mar. (24): Paraguay, Samoa, Zimbabwe, Dominica, Cameroon, Ghana, Guyana, French Guiana, Dominican Republic, Taiwan, Hong Kong, Saba, British Indian Ocean Territories, Solomon Islands, Suriname, Guatemala, Croatia, Poland, Belarus, Lithuania, Latvia, Estonia, Benin, Burkina Faso
• Apr. (28): Dominica, French Southern Territories, Costa Rica, French Polynesia, French Guiana, Guyana, Mauritania, Ivory Coast, Saba, Comoros, British Indian Ocean Territories, Mauritius, China, Slovenia, Croatia, Bosnia, Cape Verde, Nepal, Zimbabwe, Cyprus, Turkey, Niger, Jordan, Israel, Vietnam, Colombia, St. Barthelemy, Laos
• May (20): Sri Lanka, Mauritius, Tuvalu, Ivory Coast, Dominica, Niue, Brazil, Martinique, Maldives, Costa Rica, Mexico, Belize, Cayman Islands, Cuba, Saba, Cocos Islands, Niger, Kuwait, Iraq, St. Eustatius

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

China set an all-time cold record for the month of February.
Qatar set an all-time cold record for the month of March.

Hemispherical and continental temperature records in 2024

• Highest minimum temperature ever recorded in January in Asia: 28.5°C (83.3°F) at Bangkok Klong Thoey, Thailand, Jan. 14
• Highest minimum temperature ever recorded in February in Asia: 29.1°C (84.1°F) at Diego Garcia (British Indian Territories), Feb. 18
• Highest minimum temperature ever recorded in March in South America: 31.6°C (88.9°F) at Mariscal Estigarribia, Paraguay, Mar. 17
• Highest temperature ever recorded in April in Africa: 48.5°C (119.3°F) at Kayes, Mali, Apr. 3
• Highest temperature ever recorded in May in North America: 51.1°C (124.0°F) at Gallinas, Mexico, May 9
• Highest minimum temperature ever recorded in May in the Southern Hemisphere: 29.7°C (85.5°F) at Funafuti, Tuvalu, May 21

Bob Henson contributed to this post.