Key Points

• On June 22, 2017, at 5:00 p.m., 47 departments were under an orange alert and 28 under a yellow alert. The previous day, June 21, 2017, at 4:00 p.m., 67 departments were under an orange alert and 17 under a yellow alert.

• This heat wave stands out clearly for its extent, and especially for its intensity and early onset, making it a dangerous event, particularly since the population is not yet acclimated to the heat at this time of year.

• The intensity of the nighttime heat is remarkable. It prevents homes from cooling down and makes rest difficult, highlighting the influence of urban heat islands on the population’s exposure.

• On June 21, 2017, 376 emergency room visits and 214 SOS Médecins consultations for Heat-Related Illnesses (HRI) were recorded. A majority (66%) of these visits among those aged 75 and older resulted in hospitalization, compared to 29% for those aged 15–74 and 22% for those under 15.

• The increases in healthcare utilization for HRI among those under 15 and those aged 15–74 are higher than what was observed during episodes occurring in July or August in previous years.

• Given the rapid impact of heat on health, it is essential to implement preventive measures based on weather forecasts, without waiting to observe changes in health indicators.