The future of European outdoor summer sports through the lens of 50 years of the Tour de France

In this study, we consider how excessive heat, due to changing climate conditions, could affect the safety of summer sport competitions in Europe. We use the example of the world’s largest bicycle race, the Tour de France, to assess the changes in heat stress over the past five decades and discuss extreme heat protocols, data gaps and safe ways forward. We show that although July mid-day heat stress has been increasing throughout France, over recent decades the actual Tour de France race dates have so far been fortunate to avoid the hottest July days. For example, although July hourly heat stress values for Paris and its surroundings have crossed the high-risk threshold (WBGT > 28°C) on five occasions over the last 50 years, four of which occurred since 2014, this has so far not happened on the date of the Tour de France stage through Paris. Between 1974 and 2023, the hottest Parisian stage finish was in July 2002, with the hourly WBGT values staying just below the 28°C mark. However, with record-breaking heatwaves becoming more frequent, it is only a question of time as to when the race will encounter the extreme heat stress days that will test the existing heat safety protocols. We encourage the event organizers and professional teams to openly share the physiological and meteorological data in order to facilitate the development of improved and cycling-tailored heat stress indicators and thresholds. Considering the historical heat stress values, we find that the episodes of dangerous heat levels have been most common around Toulouse, Pau and Bordeaux in France’s southwest, and around Nimes and Perpignan in the southeast. Likewise, the new hotspots appear to be are emerging, with locations like Paris and Lyon starting to cross the WBGT threshold of 28°C more frequently. Morning hours remains the safest part of the day while the high heat stress can persist late into the afternoon hours. Mountain locations largely remain safe.