Key Points

• The summer of 2020 was marked by three heat waves, one of which was particularly severe in northern France. The departments affected by at least one heat wave are home to more than 50 million residents, representing 77% of the metropolitan population.

• These three heat waves had significant health impacts on the entire exposed population, including both the elderly and the young:

  • 1,924 excess deaths (+18%) were observed during periods when alert thresholds were exceeded in the affected departments. While the age group of those over 75 was the most affected (1,377 excess deaths), an increase in relative mortality was observed starting at age 45 during the second heat wave (+18%; 202 excess deaths for those aged 45–64).

  • 1,029 excess deaths were observed in the 15 departments placed under red alert for 5 days. The relative excess mortality observed in these departments is approximately five times higher than the average observed in the other affected departments.

  • Healthcare utilization was observed throughout the summer for the health indicator tracked under the PNC (iCanicule, encompassing hyperthermia, dehydration, and hyponatremia). The three heat waves accounted for 15% of emergency room visits for reasons including the iCanicule indicator (>2,000 visits) and 21% of SOS Médecin consultations (>650 consultations) during the summer. Cases of hyperthermia increased significantly during the heat waves, affecting all age groups.

• Twelve fatal workplace accidents potentially linked to heat were reported by the Occupational Health Inspection, five of which occurred during heat waves.

• These results highlight the importance of anticipating the impact of heat ahead of heatwave periods and thus reinforce the need for prevention measures tailored to the entire population, particularly during red heatwave alerts.

• During the same periods and in the same areas as the three heat waves, approximately 100 deaths linked to the COVID-19 pandemic were recorded, the vast majority of which were among people aged 70 and older. Thus, mortality linked to the COVID-19 pandemic cannot alone explain the excess mortality observed in areas impacted by heat waves, even though the COVID-19 pandemic may have increased the vulnerability of certain populations to heat.

• The summer of 2020 follows the trend of the past six years, during which increased exposure to heat waves has been observed, resulting in a rise in associated health impacts. The summer of 2020 had the greatest health impact since the implementation of the national heatwave plan in 2004, just ahead of the summers of 2015, 2018, and 2019.

• An evaluation of the implementation of the national heatwave plan—and more specifically of the management measures implemented during the summer of 2020 under red and orange alerts—would, in conjunction with the analysis of other factors such as the perception and prevention of heatwave risk in the context of the COVID-19 pandemic, social health inequalities, or the timing and characteristics of heat waves, to provide the essential insights needed to better interpret the observed health impacts.