2nd-hottest September for Earth, hottest for the U.S. » Yale Climate Connections

by Jeff Masters and Bob Henson, Yale Climate Connections
October 9, 2026

September 2026 was the planet’s second-hottest September since modern record-keeping began in 1850, NOAA’s National Centers for Environmental Information, or NCEI, reported October 9. NASA and the European Copernicus Climate Change Service also rated it as the second-hottest September, behind 2023. The global average temperature for January-September 2026 was the second-highest on record, trailing only 2024.

Global ocean surface temperatures were the warmest on record for September, while global land temperatures were the third-warmest. It was the third-warmest September on record for global temperatures estimated by satellite through the lowest few miles of the atmosphere (the lower troposphere). North America, Asia, and the Arctic recorded their warmest September on record; Oceania, its second-warmest; Africa and Europe, their fourth-warmest; and South America, its seventh-warmest.

According to NCEI’s statistical analysis, there is a greater than 99.9% chance that 2026 will rank among the three warmest years on record, but only a 0.1% chance it will be the hottest year on record. However, this statistics-based product is not designed to explicitly take El Niño or La Niña events into account, so with a record-strong global-atmosphere-warming El Niño event in full swing, it’s quite possible that 2026 will be the hottest year on record. Climate scientist Zeke Hausfather and NASA both project that 2026 will be the 1^st or 2^nd-warmest year on record, behind 2024, with 2027 likely to run away with the record. (Strong El Niño events normally peak in northern winter, and global temperature is typically higher in the second calendar year of the event than in the first one because of El Niño’s massive release of heat from ocean to atmosphere.)

Hottest September and year to date in U.S. history

The 48 contiguous United States racked up the highest average temperature for any U.S. September in data going back to 1895. It was the fourth month out of nine thus far in 2026 to set a U.S. monthly heat record, following March, July, and August. The heat was most intense in the central states: Kansas, Oklahoma, Missouri, Arkansas, and Illinois each set hottest-September records, beating even the September records set during the torrid years of the human-exacerbated Dust Bowl of the 1930s. The nation’s year-to-date average temperature (Jan.-Sep.) was also the warmest on record.

The truly record-smashing element of September wasn’t so much the weirdly hot days (although average daily highs were the fifth-highest on record over the contiguous U.S.), but the ridiculously persistent heat at night. The average daily minimum for the 48 states of 57.47°F was more than 1.2°F above the prior record from September 2019  –  a huge margin for a new record.

Nationally averaged precipitation of 2.69 inches was on the low side (33rd driest September out of the 132 years of recordkeeping), consistent with the patchy but extensive drought conditions that have plagued many of the 48 contiguous states this year. Averaged nationally, the 12-month water year that ended in September was the driest since 2000 and the 17th driest on record. Among the cities that had their driest water year in reliable records were Boulder, CO (10.50 inches), Weatherford, OK (12.23 inches), and Greensboro, NC (27.50 inches). Both Columbia, SC (28.25 inches) and Savannah, GA (28.12 inches) had their second-driest water year in unusually long datasets going back to 1887 and 1871, respectively. Among the few scattered spots with high-end moisture for the 2025-26 water year were Alpena, MI (40.67 inches, wettest in data going back to 1916) and Columbus, OH (52.48 inches, second wettest in data going back to 1878).

One notably moist region in September was in Arizona and New Mexico, which both had their second-wettest September on record. Moisture from the Pacific’s hyperactive hurricane season helped spawn frequent and intense showers and thunderstorms that led to some devastating flash floods, especially in southern New Mexico. If the record-strong El Niño now in progress leads to the classic U.S. precipitation effects over the next few months, we’re likely to see a much wetter-than-usual winter across the southern tier of states and unusually dry conditions toward the north, especially over the Midwest.

Current strong El Niño event expected to intensify and smash all-time records

An El Niño advisory continues in the Eastern Pacific, NOAA reported in its October 8 monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO. As of, weekly average sea surface temperatures in the benchmark Niño 3.4 region were at 2.1°C above average –above the 2.0°C threshold for a very strong (or “super”) El Niño event – and the three-month value for July-August-September was 1.7°C above average. Extraordinarily, subsurface temperatures remained in excess of +10.0°C (18°F) at depth in the eastern Pacific Ocean. NOAA said, “Chances remain high for a historic event that would exceed the strength of previous El Niño events dating back to 1950 (+2.5°C or more for a 3-month RONI value): the chance is 54% for September-November, 83% for October-December, and 70% for November-January.”

According to official probabilities from the NOAA Climate Prediction Center issued on September 21, it is essentially certain (100% chance) that El Niño conditions will continue through January-February-March 2027. By April-May-June, neutral conditions become the most likely outcome (54% chance, with a 45% chance of El Niño and a 1% chance of La Niña). Those April-to-June averages likely reflect a strong transition expected to be in progress during the spring. It’s worth noting that a strong El Niño event is usually (though not always!) followed by a moderate to strong La Niña event by the subsequent fall and winter, which in this case would be 2027-28.

Arctic sea ice: 13th-lowest September extent on record

According to the National Snow and Ice Data Center, Arctic sea ice extent during September 2026 was the 13th-lowest in the 48-year satellite record. On September 12, Arctic sea ice likely reached its annual minimum extent of 4.60 million square kilometers (1.78 million square miles). The 2026 minimum shares the tenth lowest spot in the nearly 48-year satellite record with 2008, 2010, and 2025. The last 20 years, from 2007 to 2026, are the lowest 20 sea ice extents in the satellite record. The Arctic experienced its third-warmest September on record.

Antarctic sea ice extent in September 2026 was the third-lowest on record. In the Antarctic, sea ice extent has been tracking near record low levels for most of the growth season, most likely reaching its maximum extent on September 14 at 17.59 million square kilometers (6.79 million square miles). If this maximum date holds, this will be the third lowest Antarctic sea ice maximum on record. The Antarctic region had above-average temperatures, which did not rank in the top 10 on record.

Notable global heat and cold marks for September 2026

Weather records expert Maximiliano Herrera has documented the records listed below in September. Follow him on Bluesky: @extremetemps.bsky.social or X: @extremetemps.

• Hottest temperature in the Northern Hemisphere: 49.0°C (120.2°F) at Red Sea Airport, Saudi Arabia, September 15;
• Coldest temperature in the Northern Hemisphere: -44.8°C (-48.6°F) at East Grip, Greenland, September 30;
• Hottest temperature in the Southern Hemisphere: 45.5°C (113.9°F) at Villamontes, Bolivia, September 20; and
• Coldest temperature in the Southern Hemisphere: -80.2°C (-112.4°F) at Concordia, Antarctica, September 17.

Twenty all-time national/territorial heat records beaten or tied as of the end of September

Chad: 48.0°C (118.4°F) at Faya, May 19 (tie)
Bahrain: 47.6°C (117.7°F) at Bahrain Airport, May 29
Jersey (UK territory): 39.3°C (102.6°F) at Maison St. Louis, June 25
Guernsey (UK territory): 36.4°C (97.5°F) at Guernsey Airport, June 25
Luxembourg: 40.9°C (105.6°F) at Reckange, June 26
Denmark: 37.0°C (98.6°F) at Odum and Odense, June 27
Germany: 41.7°C (107.1°F) at Neissemunde-Coschen, June 28
Czech Republic: 41.9°C (107.4°F) at Doksany, June 28
Poland: 40.5°C (104.9°F)at Slubice, June 28
Belarus: 40.4°C (104.7°F)at Brest, June 29
Slovakia: 41.3°C (106.3°F) at Kamenice nad Hronom, June 30; broken again with 41.4°C (106.5) at Kamenica nad Hronom, August 5; broken again with 42.2°C (108.0°F) at Dolné Plachtincy, August 6
Hungary: 42.0°C (107.6°F) at Szecseny, June 30
Uzbekistan: 49.7°C (121.5°F) at Achkuduk, July 18 (tie)
Kyrgyzstan: 44.6°C (112.3°F) at Jangy Jer, July 19
Switzerland: 39.7°C (103.5°F) at  Basel, July 30 (tie)
Liechtenstein: 38.2°C (100.8°F) at Balzers, July 30; broken again with 38.5°C (101.3°F) at Balzers, August 3
South Korea: 41.4°C (106.5°F) at Yangsan, July 31; broken again with 42.5°C (108.5°F) at Yangsan, August 2
Austria: 41.0°C (105.8°F) at Vienna Stammersdorf, August 4; broken again with 41.2°C (106.2°F) at Bad Deutsch-Alternburg, August 5
Bahamas: 36.7°C (98.0°F) at Freeport, August 14
Ecuador: 39.3°C (102.7°F) at El Coca, September 30

One all-time national/territorial cold record beaten or tied as of the end of September

Cuba: 0°C (32.0°F) at Indio Hatuey, February 3

Ninety-five additional monthly national or territorial heat records set in 2026

• Jan. (6): US Virgin Islands, Saba, Sao Tome and Principe, Congo Brazzaville, Aruba, Guadeloupe
• Feb. (7): French Southern Territories, Armenia, Iran, Turkmenistan, US Virgin Islands, USA, Honduras
• Mar. (6): US Virgin Islands, Sao Tome and Principe, USA, Guyana, Somalia, French Southern Territories
• Apr. (1): French Southern Territories
• May (12): Togo, Sao Tome and Principe, Honduras, Jersey, Guernsey, UK, Ireland, Luxembourg, Portugal, France, Andorra, Turkmenistan
• Jun. (17): Costa Rica, Antarctica, Kenya, Sao Tome and Principe, US Virgin Islands, New Zealand, UK, Switzerland, Isle of Man, Netherlands, Belgium, Austria, Lithuania, Montenegro, Slovenia, Croatia, Slovakia
• Jul. (15): Honduras, US Virgin Islands, Argentina, Uruguay, Malta, Tanzania, Costa Rica, Austria, Cuba, Paraguay, South Korea, Liechtenstein, Italy, Nicaragua, Chad
• Aug. (13): Czech Republic, Hungary, Belarus, Qatar, Honduras, Colombia, US Virgin Islands, Cayman Islands, Nicaragua, Chad, Namibia, Cocos Islands, Guadeloupe
• Sep. (18): Mongolia, Honduras, Djibouti, Andorra, France, Central African Republic, Liechtenstein, Bahrain, Costa Rica, Niger, El Salvador, Egypt, Cocos Islands, Cameroon, Tanzania, Sao Tome and Principe, Angola, Maldives

Six nations or territories have set monthly all-time cold records in 2026

• January (1): Cocos Islands
• February (2): Bahamas, Belize
• March (2): Saba, Antarctica
• April (1): Algeria

Major weather stations in September: 6 all-time heat records, 0 all-time cold records

Among global stations with a record going back to at least 1980, at least six set, not just tied, an all-time heat record in September. No stations set all-time cold records.

Palangka Raya (Indonesia) max. 37.9°C, September 23
Tanjungpandan (Indonesia) max. 36.8°C, September 24
Maripasoula (French Guiana, France) max. 38.7°C, September 24
Robore (Bolivia) max. 43.6°C, September 28
Concepcion (Bolivia) max. 40.1°C, September 29
El Coca(Ecuador) max. 39.3°C, September 30: New all-time heat record for Ecuador

Hemispherical and continental temperature records of 2026

Lowest March temperature in global history: -76.4°C (-105.5°F) at Vostok, Antarctica, March 25.
Highest June temperature and highest June minimum temperature in Antarctic history: +15.4°C (59.7°F) and +6°C (42.8°F) at Esperanza, June 5.
Highest July temperature in Europe history: 48.4°C (119.1°F) at Orani, Italy.

A full update on Hurricane Isaias is coming Friday afternoon.

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