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

August 2026 was the warmest August in the Copernicus Climate Change Service record and, within the rounding of the dataset, the joint-warmest month of any name. The global average surface air temperature was 16.96C. That is 0.85C above the 1991-2020 average for August and 0.14C above the previous August marks set in 2023 and 2024, both 16.82C.

July 2023 sits at 16.95C in the same ERA5 series. The gap between that July and this August is less than 0.01C, which Copernicus treats as a tie for the hottest month observed since the dataset begins in 1940. August 2026 was also 0.06C warmer than July 2026. In ERA5, August has beaten July in the same year only four times before: 1945, 1951, 1955 and 1985.

The 1.5C line and the ocean

Against the 1850-1900 pre-industrial estimate used for Paris Agreement comparisons, August 2026 was 1.65C warmer. It is the first calendar month since November 2025 to sit above 1.5C on that scale. One month above the threshold does not mean the Paris limit has been breached. That test is a long average. It does mean the planet has now printed another month in the zone governments said they wanted to avoid.

Sea surface temperature outside the polar oceans reached a record for August and tied the highest reading for any month. Copernicus put the extra-polar ocean figure near 21.07C, above the August 2023 mark. Global land averaged 15.73C, a whisker above the previous August land record of 15.71C set in 2024.

Samantha Burgess, strategic lead for climate at the European Centre for Medium-Range Weather Forecasts, which runs Copernicus, said the month was remarkable in both the air and the sea. She linked the extra heat to a strong El Niño stacking warm water in the tropical Pacific on top of the long-term rise from greenhouse gases. That Pacific warmth, she said, will keep feeding global averages through the rest of 2026 and into 2027.

Europe and the wider summer

June to August 2026 tied 2024 as the joint-warmest northern summer in the record. For Europe as a whole it was the third-warmest summer. For western Europe it was the warmest. August over European land averaged 20.26C, the fourth-warmest August on the continent. Rivers that move freight and cool plants, the Rhine, Danube, Vistula, Rhône and Po, ran low.

An AFP reading of the same data found that about 1.3 billion people lived through their hottest June-August on record, across 52 countries. Italy, Spain, France and Switzerland were on that list. France and Switzerland ran more than 3C above their 1991-2020 summer normals. In eight European countries, heat-linked deaths between mid-June and the end of August were counted in the tens of thousands.

Indonesia is a second face of the same pattern. Heat and drought there have fed wildfires whose emissions, from 1 to 7 September, reached 19.7 million tonnes of carbon, overtaking Russia for the week and making up more than a third of the global fire total. A Japanese military transport has now docked in Borneo with equipment for the haze fight.

What the number is not

ERA5 is a reanalysis, a blend of observations and a weather model, not a single thermometer. Other agencies will publish their own August figures in the coming days. They usually agree on the ranking even when the decimal differs. The useful point in this release is the combination of three records at once: warmest August, joint-warmest month, and a record extra-polar sea surface, arriving with an El Niño that has not yet peaked.

Burgess's warning is mechanical. El Niño typically adds heat with a lag. If the Pacific stays in this state through December, more months will clear previous highs. The 1.5C line will keep appearing in monthly tables. The policy question those tables pose is unchanged. The measurement is now sharper than it was in July 2023, because this time August, not July, carried the peak.