The historic heat wave of this second part of August finally seems to be moving away. After the late heat wave, it is now the thunderstorms that attract the attention of Météo-France. After a day of Wednesday August 23 particularly favorable to lightning, this Saturday August 26 should mark a lull.
Indeed, if all of eastern France is placed on orange alert this Friday, the start of the weekend should experience a drop in intensity in the Grand Est and Bourgogne-Franche-Comté. On the other hand, Ain, Haute-Savoie, Savoie, Isère, Drôme and Ardèche will always be on orange alert.
The country experienced its four hottest days ever recorded from Monday to Thursday after August 15, according to the national thermal indicator (daily average on 30 meteorological stations representative of mainland France and Corsica) which peaked Thursday at 27.8 ° vs.
“It is indisputable that what we are currently experiencing is a phenomenon that is already a marker of climate change,” Lauriane Batté, climatologist at Météo-France, told AFP on Thursday.
The results of this heat wave that began on August 17 at the national level and is about to end will be established by Météo-France after the weekend. It is already certain that this episode of approximately eight days will not equal the three weeks of 2006, nor the two weeks of the heat wave of 2003, the most intense to date, nor even the records of that of 2019 (the most intense day national hot weather at an average of 29.4°C and national record with 46°C in Vérargues, in Hérault).
But 2023 will go down well in the annals. First for its lateness: since 1947, only seven heat waves have been measured in France after August 15, all in the 21st century. And that of 2023 is clearly the most severe of these.
“Simulations” of future climate, given humanity’s continued greenhouse gas emissions, “show an increased likelihood of having heat waves in early and late summer,” Ms. Bat. In fact, the earliest of the heat waves was observed recently, from June 15 to 19, 2022. However, before 1989, heat waves occurred once every five years on average. Since 2000, they have been coming back every year.
If 2023 is not the worst heat wave of all periods, it is also because the northern third of the country has been relatively spared, with sometimes high but not scorching temperatures. South of a Vendée-Alsace axis, where the “heat dome” has stabilized, dozens of historic records, often from 2003, have fallen: 43.2°C in Carcassonne, 42.4°C in Toulouse, 42.6°C in Auch, 42.7°C in Orange or 41.4°C in Lyon-Bron.
“This period, with maximums exceeding 40 ° C in particular, is comparable in the South-East then the South-West to the temperatures recorded during the historic heat waves of August 2003 and June 2019”, noted Météo-France on Thursday. The 40°C threshold, measured only once in the 1960s and only once in the following decade, is now common. It was “exceeded 4 consecutive days in Carcassonne, comparable to mid-August 2003” as well as in Carpentras and Orange (Vaucluse).
