Key Points

• The first heat wave of 2026—defined as temperatures exceeding departmental alert thresholds for at least three consecutive days—affected six departments in the Brittany and Pays de la Loire regions from May 24 to 28, 2026. At least 95 excess deaths from all causes (+10.1%) were estimated for these six departments during this episode. The majority of the heat’s impact was felt by people aged 75 and older (80 excess deaths, +12.0%).
• Météo France issued an orange heat wave alert for the period from May 26 to 30, 2026, covering 17 departments in the regions of Brittany, Île-de-France, Normandy, Nouvelle-Aquitaine, and Pays de la Loire. At least 300 excess deaths from all causes (+13.9%) were estimated in these 17 departments during the warning periods. The majority of these excess deaths occurred among people aged 75 and older (230 excess deaths, +15.0%).
• These initial estimates, compiled three weeks after the end of the heatwave, are based on unconsolidated all-cause mortality data. (Data as of June 23)
• This episode, characterized by its early onset and intensity compared to normal conditions for this time of year, exposed a population unaccustomed to such heat to high temperatures during a period when school and work activities were still in full swing. The intensification of heat waves due to climate change has serious, measurable effects on public health.
• These impacts underscore the importance of implementing management and prevention measures to reduce the impact of heat on the population, without waiting to observe health impacts.