While many studies emphasize the seasonality of infectious diseases related to climatic parameters, it is crucial to keep in mind that exposure to heatwaves or cold spells have direct health impacts on populations, which results in excess mortality. This article proposes to revisit the synoptic conditions generating thermal paroxysms in Western Europe, to highlight the major events recorded over the last fifty years, and to question the physiological responses of exposure to heat or cold, as well as the importance of social vulnerability to risk.