Key Points

In mainland France, June and July 2019 were marked by two widespread and intense heat waves. During these two heat waves, for the first time since the implementation of the National Heat Wave Plan (PNC), mainland departments were placed under a red alert due to exceptionally high daytime temperatures.

In Brittany, these two heatwave episodes led to alert thresholds being exceeded in Ille-et-Vilaine and Morbihan during the first episode in June and in Ille-et-Vilaine only during the second episode. A significant impact on health was observed during these periods:

• During the periods when alert thresholds were exceeded and for the affected departments in the region, an estimated 53 [14–77] excess deaths from all causes were recorded, representing a relative excess mortality rate of +12.6%. The June heatwave, which occurred early in the season, alone accounted for 41 deaths. People aged 75 and older accounted for the majority of excess deaths (26 deaths) during both episodes.

• Heat-related conditions (defined by the iCanicule indicator, which includes hyperthermia, dehydration, and hyponatremia) accounted for 0.8% of emergency room visits and 1.3% of SOS Médecins calls during the first episode. During the second episode, this activity was lower, accounting for 0.6% of emergency room visits and 0.7% of SOS Médecins calls. During these two episodes, the hospitalization rate following an emergency department visit for a heat-related condition was 45.8% and 42.1%, respectively. While the impact was greater among those aged 75 and older, all age groups were affected.

These heat waves accounted for 29.3% of emergency room visits and 42.7% of SOS Médecins calls during the summer for the health indicator tracked under the PNC (iCanicule).