Weather alert: Gradual end of the heat wave and thunderstorms

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From Tuesday July 19 at 6:00 p.m. to Wednesday July 20 at 6:00 p.m.

Situation

This Tuesday was the maximum heat in the northeastern two-thirds of France. With the gradual arrival of an oceanic air mass, the very high temperatures will move away from our eastern borders this Wednesday, after a last tropical night.
In the south-east, the scorching temperatures will last longer.

This heat wave is linked to the passage of a depression off the coast of Brittany which brings up hot air in a southerly flow. With the circulation of this depression towards the English Channel, the wind turns to the west on the Atlantic arc, explaining the drop in temperatures.

The arrival of this cooler air now triggers thunderstorms. Late in the evening, a marked stormy deterioration is expected in the interior of Aquitaine and in the Midi-Pyrénées region, as far as Limousin. This partial degradation may be marked between 9 p.m. and midnight, to then fade as it moves up towards the central regions. The showers could locally be sustained with a risk of hail, but the watering will remain too diffuse and too short to improve the drought situation. These storms rise during the night towards the Paris basin, then, Wednesday morning, to the northeast, being scattered and of low to moderate intensity. This special press release may therefore evolve accordingly.

Observation

This Tuesday

This afternoon at 3 p.m. the most intense heat is observed from the Paris basin to Hauts-de-France with values ​​between 37 and 40°C. For example, 37.3°C was recorded at Chartres (Eure-et-Loir), 38.3°C at Châlons-en-Champagne, 38.4°C at Evreux (Eure), 38.7°C at Auxerre ( Yonne) and Troyes (Aube), 39°C in Dunkirk (North), 39.6°C in Paris Montsouris and 39.8°C in Dieppe (Seine-Maritime). The drop in temperatures is felt in the west with more than only 29°C in Bordeaux (Gironde) and 27°C in Rennes (Île-et-Vilaine). On the other hand, it is very hot from Occitania to the center-east via the Rhône valley since 37°C was recorded in Albi (Tarn) or 39.9°C in Saint-Bel (Rhône).

Late morning, the hottest regions of France are Ile-de-France, Normandy, Burgundy and Hauts-de-France with temperatures already above 30°C at 11 a.m. We already recorded 32° in Lille, 33° in Auxerre, and 34° in Évreux, Caen, Paris and Saint-Dizier, as in Provence. On the other hand, under the foggy greyness, the south-west stagnated around 22° to 25°, with already 30° in Albi in the Tarn: but in these regions (Midi-Pyrénées and Occitanie), temperatures will reach 35° to 37 ° this afternoon when the sun breaks through.

This morning :
A 09h, temperatures were rising sharply and already sometimes above 25°C in regions ranging from the Paris basin to Hauts-de-France, with:
26° in Rouen
27° in Paris
28° in Caen and Lyon
In the southwest, the temperatures were only 20° to 23°, and 24° in Toulouse, under a gray and misty sky.
Meanwhile, thunderstorms were breaking out over Finistère.

The night was tropical with temperatures not dropping below 20° to 24°C over the western half of France and in the southeast.
Thus, at daybreak, exceptional values ​​of:
30°C in Dourgne (81)
29.7°C in Longueville (50)
28° in Plerguer (35) and Menton (06)
27.7°C in the streets of inner Paris (27.5°C at the top of the Eiffel Tower)
27.3°C in Nantes
27.2°C in Dinard (35)
26.9°C in Le Havre (76)
26.6°C in Boulogne sur mer (62)

In addition, the first storms of the degradation broke out on the tip of Finistère with powerful lightning strikes on the island of Ouessant, after yesterday’s 30°C.

Yesterday Monday, dozens of monthly and absolute heat records were broken, mainly in the west of France.
Thus, with 36.7°C in Ploudalmezeau (29), the absolute record beaten yesterday is shattered today.
Nantes also broke its absolute heat record with 40.5°C, as well as Niort (40.3°C), Cholet (39.8°C), Saint-Nazaire (39.4°C), Vannes (39°C). C), La Roche-sur-Yon (39°C) or even Lannion (38.7°C).
There was also 29.5° on the island of Ouessant which could reach 30°C for the first time in its history.
In addition, there were also 41° in Biscarrosse, 38° in Bordeaux and 36° in Paris.

Sunday July 17:

At 18 o’clock, the highest temperatures reached 42.1 in Bélis (33), 40.5 in Biscarrosse (40) and nearly 40 in Bordeaux (33). The very hot weather reached Brittany with 35.2 in Brest (29) and 35.1 in Vannes (56).

Evolution

Tonight, the heat wave will gradually recede from the west, but the night remains tropical from the center to the Paris basin, Hauts-de-France and the entire east of the country. The drop in temperatures will be more significant in the west, as far as Lower Normandy and in the Loire Valley.
In the early morning of this Wednesday, the temperatures are still stuck between 20° and 23° C, especially in the northeast, as well as, in a sustainable way, on a southeast quarter and in the Rhône valley.
The heat wave alert could therefore be lifted for the north-eastern third of France because the temperatures there will no longer exceed 26° to 30° C in the afternoon, which remains hot but below the heat wave thresholds.

Storms take place especially between 8 p.m. and midnight in the interior of Aquitaine and the Midi-Pyrenees region, going up towards Limousin and western Auvergne. The strongest will burst from the Hautes-Pyrénées to the Gers, Haute-Garonne and Tarn-et-Garonne. Then, they will go up towards the central regions, losing intensity during the night, and in a rather scattered way. They could be quite marked in the first part of the night, with a risk of hail, gusts of wind and cumulative rain that could quickly reach 20 to 30 mm, but it will be quite localized.

List of departments concerned

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