After the rain in some regions, the heat wave over a large part of France? France could experience its most intense heat episode of the summer in the coming days and one of the latest ever recorded, Météo-France announced on Thursday. The hot weather has already started in the Center-East since last week.
Thursday morning, seven departments (Loire, Haute-Loire, Ain, Isère, Rhône, Savoie and Haute-Savoie) are on heat wave orange vigilance. Temperatures above 30°C are forecast over a large part of the south of the country and as far as the Rhône Valley, with peaks of up to 35 to 37°C.
And from the weekend, even warmer air will rise from the south, “minimum and maximum temperatures will go up a notch”, leading to the establishment of a heat dome. The high anticyclonic pressures will then form a kind of cover, trapping the hot air and intensifying it over the days.
“These high temperatures promise to be lasting, with peaks around 40°C over the Mediterranean South and in the Rhône Valley from this weekend”, announces Météo-France. “The heat will then spill over to the regions further north, from the Centre-Val de Loire to the North-East via the Paris Basin where we can reach 35° C,” adds the weather forecasting institute. The peak in intensity is expected early next week, Monday and Tuesday, and temperatures are not expected to return “until the middle or even the end of next week”.
Heat wave or heatwave?
Can we therefore speak of a heat wave or a heat wave? It is still a bit early to tell. To qualify as a “heat wave”, the National Thermal Index (average of daily air temperature measurements at 30 weather stations) must be greater than or equal to 25.3°C for one day, must remain above above 23.4°C for at least the next two days, and should not fall below 22.4°C. A heat wave designates an episode of high temperatures, day and night, over a period of at least three days.
In France, heat episodes occurring after August 15 are rather rare: six have occurred since 1947, all in the 21st century (2001, 2009, 2011, 2012, 2016 and 2017). “These episodes lasted between four and six days, and were shorter and less intense than the July 2022 heat waves,” notes Météo-France.
The most severe episode was that of 2012, when the highest national thermal indicator reached 26.4°C on August 19. This record could be beaten on Tuesday, according to the latest forecasts from Météo-France, which estimates that this indicator could then exceed 27 ° C.
