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 on red alert due to exceptionally high daytime temperatures.

In Hauts-de-France, only the July heatwave resulted in alert thresholds being exceeded across the entire region. On this occasion, all 5 departments were placed under a red alert for the first time (for 2 consecutive days). A significant impact on health was observed during this period:

• During the period when alert thresholds were exceeded and for the affected departments in the region, 98 [43–137] excess deaths were estimated, representing a relative excess mortality rate of +10.0%. People aged 75 and older accounted for the majority of excess deaths (51 deaths).

• Heat-related conditions (defined by the iCanicule indicator, which includes hyperthermia, dehydration, and hyponatremia) accounted for up to 3.4% of emergency room visits and 4.5% of SOS Médecins calls during this episode. The hospitalization rate following an emergency department visit during this episode was 31.4%. While the impact was greater among those aged 75 and older, all age groups were affected.

The health impacts of the heat observed were not limited to these periods alone, as two-thirds of emergency department visits and two-thirds of SOS Médecins calls occurred outside of these two heat waves, during the summer period (June 1 to September 15).