September Ranks as Earth's Second-Warmest on Record

Last month was the second-warmest September ever measured globally, according to new data from Europe's climate monitoring service, with ocean temperatures setting an outright record even as the overall air-temperature ranking fell just short of the mark set three years ago.

The average global surface air temperature in September was 16.27 degrees Celsius, 0.82 degrees above the 1991-2020 average for the month, according to the monthly bulletin published by the Copernicus Climate Change Service, the European Union's climate monitoring arm. That left the month 0.11 degrees cooler than the record set in September 2023, but still 1.63 degrees above the estimated pre-industrial average from 1850 to 1900, marking the second consecutive month this year to exceed the symbolic 1.5-degree threshold referenced in the Paris Agreement. Global land temperatures, at 13.67 degrees, were likewise the second-highest for the month on record.

Oceans told a starker story. Average sea surface temperature across the band from 60 degrees south to 60 degrees north reached 21.05 degrees Celsius, the highest September value Copernicus has recorded, coming just behind August's all-time high of 21.07 degrees. The bulletin noted that daily sea surface temperatures outside the polar regions have run at record levels for every calendar day since June 19, an unbroken streak of more than three months. The El Niño-linked Niño 3.4 region of the tropical Pacific posted a September sea-surface anomaly of 2.99 degrees above average, a record for the region that surpassed the previous mark of 2.81 degrees set in December 1997, underscoring how strong this year's El Niño pattern has become.

Separate figures from the U.S. National Oceanic and Atmospheric Administration's monthly global climate report point to the same conclusion using a different historical baseline. Coverage of that NOAA report, including an account carried by The Weather Channel, put global land-and-ocean temperature at 1.33 degrees Celsius above NOAA's 20th-century average, also the second-highest September in that agency's record dating to 1850, and noted the month marked the 51st consecutive September with global temperatures above the long-term average. The contiguous United States, meanwhile, had its own warmest September on record, surpassing the previous mark set in 1998. NOAA and Copernicus calculate their anomalies against different reference periods, which produces different headline numbers, but the two agencies' findings this year point in the same direction. Background on how NOAA tracks these monthly comparisons is available through the agency's climate.gov public information service.

In Europe specifically, Copernicus found the continent's land temperature averaged 16.26 degrees, 1.54 degrees above the seasonal norm and the third-warmest September in the Copernicus record, while Western Europe tied 2023 for its warmest September on record at 2.51 degrees above average. The pattern of warmth was not confined to Europe: the bulletin's broader data also pointed to unusual heat across parts of North America and Asia during the month.

Taken together with the rest of the year, the September data keeps 2026 on course to rank among the handful of warmest years ever recorded. Copernicus found that the January-through-September period this year was the second-warmest such stretch on record, trailing only the equivalent months of 2024 and running ahead of both 2023 and 2025. A summary of the trend published by The Weather Channel noted that forecasters expect the current El Niño to keep strengthening into early 2027, a pattern that typically pushes global temperatures higher still in its wake. Scientists caution that where 2026 ultimately ranks will depend heavily on conditions over the final three months of the year, but the trajectory so far has left little doubt that the decade's run of record or near-record years is continuing.