Clotilde Dumay, edited by Gauthier Delomez 8:55 p.m., August 16, 2022

France is preparing for a wave of storms: eight departments have been placed on orange alert, in the south of the country.

Heavy rain is expected in the night, and it should fall the equivalent of a month of rain.

Europe 1 deciphers this phenomenon called the Mediterranean episode with a specialist from Météo France.

On the night of August 16 to 17, several French departments bordered or close to the Mediterranean Sea will experience a Mediterranean episode.

From 80 to 100 mm, or even 150 mm locally, of precipitation is expected overnight, particularly in the eight departments placed on orange vigilance for thunderstorms and for rain floods.

This represents the equivalent of a month of rain.

This phenomenon generally occurs when the sea temperature is warm, but there are also other factors that come into play. Europe 1 takes stock with Frédéric Nathan, forecasting engineer at Météo France.

A threshold from 100 mm of rain

"It is first of all the meteorological situation that plays", he indicates to Europe 1. "The fact that the Mediterranean is hot does not necessarily lead to Mediterranean episodes. There must be a meteorological situation which is adapted, that is to say the arrival of cold air from altitude which comes from the south of Iceland, which arrives on the west, slides most often on Spain and enters confrontation with the very hot Mediterranean air", specifies Frédéric Nathan.

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The meteorologist continues: "The Mediterranean episode is when we start to have stationary cells, that is to say storms that last quite a long time and which give strong accumulations of rain."

According to him, "from thresholds of more than 100 mm locally, we can estimate that it is a Mediterranean episode, fairly classic despite everything, stormy summer, which we have already experienced in the past."

Frédéric Nathan thus evokes dates in 2018, 2010 or even 2006. "It happens from time to time."

In addition, Météo France does not exclude the arrival of a new heat wave from the middle of next week, over half of the country.