August 2026 ties July 2023 as Earth's hottest month on the ERA5 record

August 2026 was the warmest August in the Copernicus ERA5 record and the joint-warmest month of any name, tied with July 2023. The global surface air temperature averaged 16.96C. That is 0.85C above the 1991-2020 August mean and 1.65C above the 1850-1900 baseline Copernicus uses as a pre-industrial stand-in. The gap with July 2023, recorded at 16.95C, is less than 0.01C.

The same month was 0.06C warmer than July 2026. July is usually the hottest calendar month on the planet because more land sits in the Northern Hemisphere and land heats faster than ocean. ERA5, which starts in 1940, has seen August beat July in the same year only four times before: 1945, 1951, 1955 and 1985.

Land, sea and the 1.5C line

August was the first month since November 2025 to sit more than 1.5C above the 1850-1900 estimate. The United Nations said last week that a consistent breach of that Paris reference is now unavoidable. A single month above 1.5C is not the 20-year average the treaty text uses. It is still a marker. It tells anyone reading a monthly bulletin that the short-term climate has crossed a line the policy process still treats as a long-term goal.

Global land in August averaged 15.73C, a fraction above the previous August land record of 15.71C set in 2024. Extra-polar sea surface temperature, measured between 60 degrees south and 60 degrees north, averaged 21.07C. That is the highest August ocean reading on record, above 20.98C in August 2023, and it ties March 2024 as the highest ocean month of any name. The highest daily extra-polar sea surface temperature in the series reached 21.11C.

NOAA's separate analysis, published from Asheville, put August 0.08C above the previous joint August records of 2023 and 2024 on its own baseline. It called August the 48th straight August above the twentieth-century average. The last cooler-than-average August in that series was 1978. All ten of the warmest Augusts have arrived since 2016. NOAA said North America and Africa had their warmest August on record. Asia had its second-warmest. No land or ocean region set a record-cold August.

El Nino on top of the long trend

Copernicus attributed the spike to two stacked effects: the long rise in greenhouse gases from fossil fuels, and a strengthening El Nino that has pushed warm water to the surface of the equatorial Pacific. That Pacific heat will spread through the rest of the climate system into late 2026 and 2027. Samantha Burgess, strategic lead for climate at ECMWF, used the bulletin to stress that the ocean record and the air record arrived together.

Summer 2026, June to August, tied 2024 as the joint-warmest boreal summer globally. Europe as a whole had its third-warmest summer. Western Europe had its warmest. The contiguous United States, in NOAA's figures, averaged 75.6F in August, 3.5F above the twentieth-century mean, the hottest August in that national series.

What the next bulletins will test

A tie at the level of 0.01C can move when datasets are revised. ERA5 and NOAA do not use the same baseline or the same blend of stations, buoys and satellites. Both, this month, point in the same direction. The useful number for readers who already saw the headline is not that August was hot. It is that August was hotter than July, that the extra-polar ocean matched its all-time monthly peak, and that the 1.5C monthly anomaly has returned before El Nino has finished its work.

If the Pacific stays warm into the northern winter, the next candidates for a new monthly record sit in late 2026. The Copernicus series will show that first in the daily extra-polar sea surface temperature, then in the monthly air average. Those two lines are now close enough that a single warm ocean week can decide which month holds the mark.