Heatwave: Why is the southern Rhone Valley often the hottest spot in France?

As a sign that France was going to warm up, the Rhône, Drôme and Ardèche were placed on Monday, August 21, in heat wave red vigilance. These three departments were followed on Tuesday by Loire, Isère, Vaucluse and Gard. With the exception of Bouches-du-Rhône, all the departments making up the Rhône Valley have been placed at the last stage of vigilance, because “the persistence, duration and intensity of temperatures require and oblige to extend the measures protection of populations”, explained Christophe Béchu, Minister of Ecological Transition.

For the Rhone Valley to be affected by high temperatures, three factors must be present. There is, first, “sufficient sunshine”, with the peak usually being reached “late June, early July”. Unlike the departments located further north, the region benefits from strong sunshine this year.

Then there is a “rather low soil moisture.” Here, the peak is reached in August, because “the soils are drying out due to prolonged high temperatures”, he continues. And the drought, down to its lowest level since early 2022 in Europe in early August, continues to seriously affect the valley.