September 2025 was the third-warmest September globally, with an average surface air temperature of 16.11°C, 0.66°C above the 1991-2020 average for September.

That's according to the latest publication by the Copernicus Climate Change Service (C3S), implemented by the European Centre for Medium-Range Weather Forecasts on behalf of the European Commission.

It routinely publishes monthly climate bulletins reporting on the changes observed in global surface air and sea temperatures, sea ice cover and hydrological variables.

Most of the reported findings are based on a dataset using billions of measurements from satellites, ships, aircraft and weather stations around the world.

September 2025 was 0.27°C cooler than the warmest September on record, in 2023, and only 0.07°C cooler than September 2024.

Last month was 1.47°C above the estimated 1850-1900 average used to define the pre-industrial level.

According to strategic lead for climate, Samantha Burgess: “The global temperature in September 2025 was the third warmest on record, nearly as high as in September 2024, less than a tenth of a degree cooler.

"A year on, the global temperature context remains much the same, with persistently high land and sea surface temperatures reflecting the continuing influence of greenhouse gas accumulation in the atmosphere."

European climate in September

The average temperature over European land for September 2025 was 15.95°C, 1.23°C above the 1991-2020 average for September, ranking fifth highest on record for the month.

This was only marginally different (within 0.04°C) from the fourth warmest in 2018 and the sixth warmest in 2011.

The most pronounced above-average air temperatures were recorded over Fennoscandia and eastern Europe.

Cooler-than-average temperatures were seen only over parts of western Europe and were typically less than one degree cooler than average.

Outside Europe, temperatures were most above average over Canada, parts of Greenland, northwesternmost Siberia and adjacent coastal regions, as well as large parts of Antarctica.

The only large regions globally with pronounced negative temperature anomalies were northern central Siberia, western Australia, and parts of eastern Antarctica.

In September 2025, it was wetter than average in north-western and central Europe, Fennoscandia, along the eastern Black Sea coast, and in parts of Italy and coastal regions of Croatia and eastern Spain.

In some cases, heavy rainfall caused flooding and associated disruptions.

Most of the Iberian Peninsula, the Norwegian coast, much of peninsular Italy, the Balkans, as well as parts of Ukraine and western Russia were drier than average.

Beyond Europe, wetter-than-average conditions were experienced in the south-western and central US, Alaska, north-western Mexico, and in regions of Brazil, Argentina and Chile.

It was also wetter than average in the Northern Horn of Africa, the southern Arabian Peninsula, Pakistan, and north-western India, central Asia, and eastern China.

In many of these regions, heavy precipitation led to flooding, often associated with the transit of tropical cyclones.

It was drier than average in parts of Canada, eastern US, north-eastern Mexico, northern and easternmost Russia, and north of the Indian subcontinent, as well as in Uruguay and part of Brazil.