Second Warmest September on Record as Oceans Hit 1.63°C

September 2026 was the second warmest September in the global record, the European Union's Copernicus Climate Change Service said in its monthly climate bulletin this month. The global average surface air temperature reached 16.27 degrees Celsius, which put the month 0.82 degrees above the 1991 to 2020 average and 1.63 degrees above the estimated pre-industrial baseline of 1850 to 1900.

The month fell just short of the all-time September record. September 2023 remains the warmest September in the ERA5 dataset, by a margin of 0.11 degrees, according to the service, which is run by the European Centre for Medium-Range Weather Forecasts. The dataset is a reanalysis of decades of weather observations, and the bulletin plots this year against the three warmest calendar years it contains.

August crossed the same threshold, making them the first consecutive pair of months above the one-and-a-half-degree mark since November 2025. The service expects the streak to continue into 2027, driven in large part by the Pacific.

The extra-polar oceans set their own record. The average sea surface temperature across the oceans outside the polar regions reached 21.05 degrees Celsius in September, topping the previous monthly record of 20.92 degrees. The service ties the record to a strengthening El Niño in the equatorial Pacific, which pumps heat from the ocean into the atmosphere and nudges the global average upward.

El Niño keeps strengthening

In the Niño 3.4 region of the equatorial Pacific, the sea surface temperature averaged 29.70 degrees Celsius for the month, a record for that patch of ocean. The World Meteorological Organization has said the event could become the strongest El Niño since observations began in 1950. Its seasonal outlook puts the anomaly in the region at about 3.7 degrees above normal for October through December, well clear of the roughly 2.6-degree peak recorded in late 2015 and early 2016, with the strongest point most likely arriving around December.

Events of this strength tend to rearrange rainfall for months after they peak. Climate scientists expect heavier downpours in some regions and prolonged drought in others as the pattern matures, and the bulletin notes that sea surface temperatures are likely to stay elevated well into next year. The Hindu BusinessLine, reporting on the same bulletin, described intensifying climate extremes as temperatures are forecast to remain elevated through the coming months.

Sustained heat of this kind carries practical costs beyond the charts. Hotter months raise health risks during heatwaves and strain water and power supplies, pressures that were already visible across Europe's dry farmland and low rivers this summer.

Dry Europe, low ice around Antarctica

Across Europe, the unusually warm and dry summer carried into September. It was the continent's third warmest September, while western Europe recorded its joint warmest September, matching the previous record. Average land temperatures across Europe stood at 16.26 degrees, the service said, 1.54 degrees higher than the recent 30-year norm.

Dry conditions deepened across Iberia, France, Italy, the western Balkans and Greece compared with August, and river flows ran exceptionally low in parts of the Rhine, Danube, Vistula and Garonne-Dordogne, according to the bulletin. Wetter-than-average weather reached parts of northern and northeastern Europe and Türkiye, but it did little to change the continental picture.

Around Antarctica, sea ice sat near a record low. The winter maximum extent came in at one of the smallest levels on record, the bulletin said, continuing a run of weak ice seasons at the southern pole.

The service's director, Carlo Buontempo, said in a statement that September was "the second warmest on record globally," with exceptionally high temperatures returning to parts of Europe after an extreme summer. He described a new run of months above that threshold that was likely to last into next year, and said crossing the Paris Agreement's long-term warming limit was "only a matter of time," while the scale and duration of the overshoot remained a matter of choice.

Monthly figures are not the same as the Paris Agreement's limit, which is judged on long-term averages rather than a single hot month, a distinction explored in recent analysis of warming's human fingerprints. The next Copernicus bulletin, due in early November, will show whether October kept the streak alive.