Climate

Outdoor heat stress

How many more or fewer days than usual brought strong heat stress outdoors in 2025, on land worldwide except Antarctica.

Climate 2025 C3S

What it is

The Copernicus Climate Change Service offers a dataset of thermal comfort indices, produced by the European Centre for Medium-Range Weather Forecasts from its atmospheric reanalysis, which combines model data with observations from across the world into a complete and consistent description of the climate. One of them is the Universal Thermal Climate Index, a feels-like temperature in degrees Celsius that combines air temperature, humidity, wind and radiation. The data cover the globe except Antarctica on a 0.25 degree grid, from January 1940 to near real time. A day with at least strong heat stress is a day on which the feels-like temperature reaches 32 °C or more.

Why it matters

In 2025, 50% of the globe's land, excluding Antarctica, had more days than average with at least strong heat stress. In parts of the southern United States and eastern Asia there were up to 45 more such days than average, and central Africa had up to around 110 more days with very strong heat stress, a feels-like temperature of 38 °C or above. Most of Australia and parts of northern Africa and the Arabian Peninsula had more extreme heat stress days than average. Up to a third of the globe, including southern Africa and southern Asia, had fewer heat stress days than average.

How to read it

Each colour shows how many days more or fewer than the 1991 to 2020 average had at least strong heat stress in 2025. Brown and orange mean more days, near white and cream mean close to the average, and purple means fewer days. The stronger the colour, the larger the difference. The ocean and Antarctica are left blank.

Limits

The feels-like temperature is calculated from reanalysis output on a 0.25 degree grid, and Antarctica is outside the dataset. The map shows only the change in the number of days compared with the 1991 to 2020 average. The heat stress categories begin at 26 °C for moderate, 32 °C for strong, 38 °C for very strong and 46 °C for extreme. Downloading the gridded data needs a free account of the Copernicus Climate Data Store.

Sources

License

Map: Fix Planet, from the map of the Copernicus Climate Change Service and the European Centre for Medium-Range Weather Forecasts in the Global Climate Highlights 2025 report, based on the Universal Thermal Climate Index from the reanalysis of the European Centre for Medium-Range Weather Forecasts. Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor the European Centre for Medium-Range Weather Forecasts is responsible for any use of the information. Licence: Copernicus.

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