Key Points

The summer of 2019 was marked by two widespread and intense heat waves, with alert thresholds exceeded between June 24 and July 7 and between July 21 and 27. During these two heat waves, for the first time, 4 and 20 departments, respectively—representing 7% and 35% of the French metropolitan population—were placed under a red alert due to exceptionally high daytime temperatures.

These two heat waves had health impacts on the exposed populations. These impacts affected the entire population, including both the elderly and the young:

• 1,462 excess deaths (+9.2%) were observed during the periods when alert thresholds were exceeded in the affected departments. While the age group of those over 75 was the most affected, the 15–44 and 65–74 age groups were also impacted.

• 572 excess deaths were observed in departments under red alert. Excess mortality in these departments is approximately 50% higher than the average for affected departments.

• These heat waves account for 49% of emergency room visits (>10,000 visits) and 65% of SOS Médecin consultations (>3,500 consultations) during the summer for the health indicator tracked under the PNC (iCanicule, encompassing hyperthermia, dehydration, and hyponatremia). Cases of hyperthermia increased significantly during heat waves, affecting all age groups.

Ten workplace deaths potentially related to heat that occurred during the two heat waves were also reported.

Prevention of the impact of heat must be planned in advance of heatwave periods and reinforced during them. These results reinforce the need for prevention measures tailored to the entire population, particularly during red heatwave alerts.