Key Points

• A heat wave hit France at the end of the week of June 25, 2025. In Brittany, the heat wave began on Thursday, June 19: Ille-et-Vilaine and Morbihan were placed under a yellow heat wave alert. On Friday, June 20, these two departments were placed under an orange heat wave alert, while the Côtes d’Armor and Finistère departments were placed under a yellow alert until Saturday, June 21. On Sunday, June 22, all Breton departments returned to a green alert.

• A regional analysis of emergency care utilization indicates an increase in the iCanicule composite health indicator (including hyperthermia, dehydration, and hyponatremia) during week 25/2025, concentrated in the period from June 18 to 21.

• A regional analysis of calls to SOS Médecins indicates an increase in the iCanicule composite health indicator (including heatstroke and dehydration) during week 25/2025, concentrated in the period from June 19 to 22.

This trend falls within the expected fluctuations for the weekend’s weather conditions and is observable across the region as a whole.