July 25, 2021

Weather Alert: Very hot episode

Through Cyrille DUCHESNE, meteorologist

Very hot episode

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From Monday June 14 at 12:00 p.m. to Thursday June 17 at 9:00 a.m.

Situation

Until next Wednesday or Thursday depending on the region, a period of very hot weather sets in France. This is the first episode of strong to very strong heat this year 2021 in connection with the presence of a high pressure system which is pushing up a mass of air from North Africa. The southern regions are particularly affected by this influx of tropical air. For 3 to 4 days, the temperatures in the departments placed in alert level reach or are slightly below the heatwave thresholds, which explains the yellow and not orange level of this alert. At night, the strong heat that will have accumulated during the day will have difficulty in being evacuated in the big cities.

This episode of very strong heat is exceptional by its precocity. Perpignan broke a heat record on Sunday for the first half of June with 37.1 ° C in the shade! The intensity of this heat wave is remarkable even if the monthly records for June cannot be broken after the exceptional heatwave period which affected the south of the country at the end of June 2019 (up to 46 ° C in the shade in Vérargues in the Hérault).

Observation

This Monday at noon, Perpignan is once again the hottest city in France with 35 ° C in the shade! The city of Durban-Corbières in the Aude follows closely with 34 ° C then Narbonne with 33 ° C. The 30 ° C has just been reached in Bordeaux.

Monday morning, minimum temperatures were generally between 20 and 24 ° C in Languedoc-Roussillon. So the night was tropical; minimum temperatures were 20.5 ° C in Nîmes (30), 21.5 ° C in Perpignan (66), 22.9 ° C in Leucate (11), 23.4 ° C in Gruissan (11) and 24 ° C in Sète (34). In the southwest, minimum temperatures were generally between 15 and 20 ° C.

Sunday afternoon, the heat was particularly strong in Languedoc-Roussillon with 37.8 ° C observed in Céret (66), 37.1 ° C in Perpignan (66) and 36.8 ° C in Béziers (34). These are heat records for the second ten days of June in these cities. It was also very hot in New Aquitaine with 35.3 ° C in Navarrenx (64), 35.1 ° C at Cap Ferret (33), 33.7 ° C in Toulouse (31) or 33.1 ° C in Bordeaux.

Evolution

After one night from Sunday to Monday very mild to see tropical in the towns of the departments on alert, the very hot weather resumes from the southwest in Languedoc-Roussillon with 34 to 38 ° C in the shade this Monday afternoon. These high temperatures, of less intensity, reach the central regions as far as the Rhône-Alpes region, then up towards the Paris basin with 30 to 33 ° C.

Mardi and especially Wednesday will be the hottest days of the week at the national level with maximums between 33 and 36 ° C over 2/3 of the country, and peaks at 37/38 ° C from the southwest to the center-east of the territory. These very hot weather will also reach the Paris region, the Strasbourg region and the Lille region with 34 ° C Wednesday afternoon.

From Thursday, temperatures will drop in the west as thunderstorms pass. The episode of very hot weather will end in the west but it will continue in the east of the country until Friday.

Characteristics of this episode of high heat

– more than 3 consecutive days with maximum temperatures at or slightly below the heatwave thresholds with 33 to 35 ° C and peaks around 37-38 ° C in the shade in the southwest and in Languedoc-Roussillon .

– very mild nights with minimums that will have difficulty falling below 18 to 23 ° C in large cities, a little less in the countryside with 16 to 19 ° C.

List of departments concerned