Ahead of Heat Action Day, this new report from scientists at World Weather Attribution, the Red Cross Red Crescent Climate Centre, and Climate Central assesses the influence of human-caused climate change on dangerous heat waves over the past 12 months (May 1, 2024, to May 1, 2025).
The period of analysis spans Earth’s hottest year and hottest January ever recorded. The report found that human-caused climate change is boosting dangerous extreme heat for billions of people, and making heat events longer and more likely.

Key findings from the report include:

• Over the 12-month period, 4 billion people — about 49% of the global population — experienced at least 30 days of extreme heat (hotter than 90% of temperatures observed in their local area over the 1991-2020 period).
• In 195 countries/territories, climate change at least doubled the number of extreme heat days, as compared to a world without climate change.
• All 67 extreme heat events — identified as significant based on record-setting temperatures or major impacts to people or property — were found to be influenced by climate change.

This report also demonstrates the crucial role of tracking and reporting on extreme heat impacts and offers actionable solutions to heat risk.

See the full report, produced in collaboration by Climate Central, World Weather Attribution, and the Red Cross Red Crescent Climate Centre.

Major funding provided by the Bezos Earth Fund