August 2026 ties July 2023 as the hottest month in the instrumental record

August 2026 was the warmest August in the ERA5 record and the joint-warmest calendar month ever measured, tied with July 2023, the Copernicus Climate Change Service said. The global surface air average was 16.96 C, 0.85 C above the 1991-2020 August mean and 1.65 C above the estimated pre-industrial baseline. July 2023 stood at 16.95 C. The gap is less than 0.01 C.

August was 0.06 C warmer than July 2026. In ERA5, which starts in 1940, August has beaten July in the same year only four times before: 1945, 1951, 1955 and 1985. July is normally the warmest month on the planet. It was not this year.

The month was also the first since November 2025 to sit more than 1.5 C above the pre-industrial line. Samantha Burgess, strategic lead for climate at ECMWF, said people have not lived through a summer this warm in the past 100,000 years. That claim rests on paleoclimate reconstructions, not on thermometers. The thermometer record is clear enough on its own.

The ocean did more of the work

Average sea surface temperature across the extra-polar ocean, 60 S to 60 N, was 21.07 C in August, the highest August value on record, above 20.98 C in August 2023. Daily extra-polar SST has set a calendar-day record every day since 19 June. On 24 and 25 August the daily figure reached 21.11 C, above the previous all-time daily mark of 21.09 C set in March 2024.

Those numbers reflect two things at once: the long rise from greenhouse gases, and a rapidly building El Niño in the equatorial Pacific. Forecasts used by Copernicus say the 2026 event may outgrow the 2023 Niño. NOAA has put the chance of a very strong event this Northern Hemisphere autumn and winter above 90 percent, and a 69 percent chance that the October-December relative Niño index reaches at least +2.5 C, which would beat every event in NOAA's series back to 1950.

If the last four months of 2026 are as warm as the same months in 2023, the annual average would sit close to 2024, the current warmest year. Burgess has said some coming months could run as much as 2 C above the pre-industrial mean.

Where the heat sat

Western Europe and the United States had their hottest summers in the overlapping Copernicus and NOAA sets. Atlantic and western Mediterranean waters were in strong or severe marine heatwave conditions. High Pacific temperatures are already feeding seasonal fires in Indonesia, according to the Copernicus Atmosphere Monitoring Service.

The Atlantic hurricane season, by contrast, reached mid-September with no hurricane, the first such blank at this date since 1941. Almanaque recorded that fact on Saturday. A quiet cyclone basin and a record-warm ocean can sit in the same month. They are not a contradiction. They are two outputs of the same heat budget, routed through different basins.

The next test is September through December, when El Niño usually peaks. The August file is already closed. It is tied at the top of the chart with July 2023, and the water under that air is still warming.