Heat Waves and Health: Excess Mortality. Bulletin of September 11, 2025.

Key Points

  • From August 8 to 19, mainland France and Corsica experienced a heat wave notable for its duration and intensity, particularly from the Southwest to the Central-East. This second heat wave of the summer affected 41 departments, representing 40% of the resident population in mainland France.

  • At least 280 excess deaths from all causes (+4.7%) were estimated during this heatwave in the affected departments. This excess mortality was observed only among people aged 75 and older.

  • This initial estimate, produced three weeks after the end of the heatwave, is based on unconsolidated all-cause mortality data (data as of September 9). The complete estimate of excess all-cause mortality linked to this heatwave, supplemented by the estimate of heat-attributable mortality, will be available in the summer report published in the fall after the end of the monitoring period.

  • The observed health impacts underscore the importance of implementing preventive measures to mitigate the impact of heat, not only during heat waves but throughout the summer, and the need for a strengthened climate change adaptation strategy at both the national and regional levels.

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