The Heat Wave and Health Alert System (SACS), established by Santé publique France, enables the assessment of the health impacts of heat waves.

Situation Update During an Alert

During a heat wave alert, Santé publique France analyzes city emergency data (SOS Médecins) and hospital emergency room data daily. Since 2023, 15 days after the end of each heat wave, Santé publique France publishes a weekly epidemiological report including an initial estimate of excess all-cause mortality observed during the heat wave. Once the alert has ended, Santé publique France assesses the heat wave.

Impact of Heat on the Summers of 2017–2025

Over the past nine summers, 11,700 deaths have been attributed to the population’s exposure to heat during heat waves, and nearly 40,000 for the entire monitoring period.

Thus, nearly 30% of heat-related deaths are associated with heat waves, which account for only 4% of the days in the monitoring period. Mortality attributable to summer heat is higher in 2025 than in the previous summer but falls between 2022 and 2023, which were meteorologically hot summers (the 2nd and 5th hottest summers since 1900). Each summer and each heatwave episode has its own characteristics in terms of duration, intensity, and exposed population, making comparisons with previous years complex. However, it is observed each year that heat accounts for 1 to 4% of summer mortality and 7 to 12% of mortality during heatwaves, figures that have remained stable since 2017.

At the national level

• Heat and Health. Summer 2025 Report. | Infographic

Increased use of emergency rooms for heat-related illnesses

During the summers of 2015 through 2024, more than 155,000 emergency room visits and more than 33,000 SOS Médecins consultations were recorded in the SurSaUD® emergency and death surveillance system for metropolitan France, regarding the composite indicator tracked as part of the heat wave health management system (iCanicule), which includes heatstroke or hyperthermia, dehydration, and hyponatremia.

The use of emergency care for the iCanicule indicator is observed throughout the summer, including outside periods of yellow, orange, or red heat wave alerts: thus, in recent years, up to 85% of emergency room visits and up to 80% of SOS Médecins consultations occurred outside alert periods. However, peaks in emergency care use for iCanicule are observed during periods when a large portion of the population is subject to a heat wave alert.