Paris, Lyon, Grenoble, Bordeaux… cities in search of fresh ideas to combat heatwaves

No wind, blazing sun, and the feeling of living in an open-air oven. On Saturday, June 21, the first heatwave of 2025, particularly early , will reach a torrid peak in France: 37°C in Lyon, 38°C from Bordeaux to Tours, and even 39°C in Rennes. For several days now, exceptionally high temperatures for the season have been heating up cities. This weekend again, the thermometer will not drop below 20°C in the middle of the night, which will be described as "tropical" in many areas. In their bulletins, Météo France forecasters take into account this particularly harmful phenomenon of nighttime overheating: the urban heat island.

Thus, in the capital during a heatwave, it can be up to 10°C warmer at night than in the suburbs; during the day, the difference is only 1 to 2°C. "As soon as the sun sets, the countryside cools down, but not the city, because the buildings and streets have stored the heat and release it. During the first two or three hours of the night, we observe the greatest difference. This increases health risks: the ap