August 2026 ties for the hottest month in the Copernicus record

How exceptional was August’s heat? To answer without confusing a local heat wave with the state of the planet, the Copernicus Climate Change Service compared global average near-surface air temperature with other months. Its assessment, released on September 10, places August 2026 at the top of the ERA5 record, which begins in 1940, tied with July 2023.

The comparison uses a reanalysis: observations are combined with a physical model of the atmosphere to reconstruct conditions on a grid covering the planet. The team calculates averages over the month and compares equivalent periods. This is neither a reading from a single thermometer nor the highest temperature reached on an afternoon.

The estimated global average for August was 16.96°C, or 0.85°C above the average for August in 1991–2020. The previous August records belonged to 2023 and 2024. When all calendar months are included, Copernicus considers August 2026 and July 2023 tied: the difference between the unrounded values is less than 0.01°C.

The same assessment examined sea surface temperature separately. Across the ocean between 60° south and 60° north, excluding the polar regions, the August average reached 21.07°C, a record for that month in ERA5. This measures water, not air. Copernicus links the ocean heat to developing El Niño conditions in the equatorial Pacific and exceptionally high temperatures in other basins. The natural fluctuation operates in a climate already warmed by human greenhouse gas emissions.

Another comparison places August 1.65°C above the estimated average for the same month in 1850–1900. That reference period, before intensive industrialization, is not the one used to calculate the 0.85°C departure. Nor does one month above 1.5°C amount to exceeding the Paris Agreement’s limit, which concerns warming over decades.

The findings bring together two signs of exceptional heat, in air and water, without making them interchangeable measures. For climate monitoring, the persistence of that heat matters, not just a month’s position in a ranking. The January–August assessment places 2026 as the second-warmest year over that interval; the full-year ranking still depends on the remaining months.