Weather alert: Heat wave and violent storms, risk of hail

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From Tuesday, June 21 at 3:00 a.m. to Tuesday, June 21 at 10:00 p.m.

Situation

The episode of strong heat continues until Tuesday in the center-east of the country.

The minimum temperatures are between 20 and 24°C on average. They have trouble descending at night because of the sustained southerly wind. During the day, strong to very strong heat persists with generally 33 to 36°C.

At the same time as this heat wave, and in connection with a low-moving depression over the near Atlantic, punctually strong thunderstorms are developing this Monday evening from Aquitaine to Limousin and can be accompanied by hailstorms. Locally, accumulations of 50 mm of water, or even more, are possible. Beware, also, of strong gusts under these storms (>90 km/h).

Observation

Night from Monday to Tuesday:

Storms are quite widespread in the center-west of France, which can be accompanied by abundant accumulations of rain and hailstorms, especially between Périgord and the central region.

This Monday

At 6 p.m., thunderstorms were forming in the Bay of Biscay, off the Aquitaine coast. They were starting to go up towards the Charentes.
The highest temperatures, scorching, were recorded in the center-east with 37°C at Lyon Tête d’Or and 35°C at the Lyon-Bron station. 37°C also in Villefranche sur Saône (69), 37.4°C in Balbigny (42), and 35.4° in Saint Chamond (42).

A 15h, the strong heats concern the center-east and the south-east of France. We observe 32°C in Mâcon, 33°C in Saint-Etienne and Montélimar, 34°C in Lyon, Grenoble. With a very low humidity rate (20 to 40%) and a sometimes strong southerly wind, the feeling is not too heavy but the risk of fires is maximum.

A 12h, the high temperatures concern all the departments on orange alert with already 30°C in Saint-Etienne and 31°C in Lyon. The warm southerly wind is moderate, but adds discomfort. On the other hand, the humidity is very low, between 25 and 40% on average. Attention to the risk of fire which is maximum this afternoon.

A 9h, the heat is already present in the center-east after a torrid night. Temperatures fluctuate between 24 and 26°C in general. For example, it was 26°C in Lyon Bron and Saint-Etienne.

Evolution

Heat wave parameter

Night from Monday to Tuesday

It is a new tropical night which occurs with lows often above 20°C in large cities, but also in the countryside, due to the southerly wind which is maintained and which stirs the air, preventing the usual “holes cold” to cool down. These high temperatures are painful to bear, especially in urban areas that retain heat.

This Tuesday

This is the last day of strong heat in the center-east with values ​​still reaching 32 to 36°C during the afternoon. Note that strong thunderstorms are expected at the end of the afternoon and in the evening. They will put an end to this heat wave episode.

Storms parameter

Night from Monday to Tuesday

The strong thunderstorms progress from Charentes towards the Centre-Val de Loire, but gradually lose intensity at the end of the night heading towards the Paris basin. At that time, they can still cause heavy rains in the south of Ile-de-France with lightning strikes, but the risk of hail disappears.

This Tuesday evening:

New storms, potentially strong, will break out in the center-east but also in the Pyrenees: in the evening, the regions between the central Pyrenees and Auvergne-Rhône-Alpes will be affected by these violent storms, which may cause hailstorms as well as sudden gusts of wind between 80 and 100 km / h, in a localized way. This special release will then be extended to other departments.

List of departments concerned

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