In one week, the French territory lost between 10 and 25 ° C approximately, going from near-summer temperatures to a return to winter despite the beginning of April.

On Europe 1, Sébastien Leas, forecaster at Météo France, explains the reasons for these radical changes.

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We no longer know how to dress: after the near-summer temperatures of last week, sometimes reaching 26 degrees and with heat records in more than 200 cities, we expect only 5 ° C this Monday afternoon in Lille, 12 ° C in La Rochelle or 10 ° C in Paris and even the return of frost in some areas.

How to explain this big gap?

Météo France forecaster Sébastien Leas gives explanations on Europe 1. According to him, there could be up to 25 ° C difference in a week due to a change in air masses.

From the air of the Sahara to the arctic air

"This large difference can be explained quite easily since we completely change the air masses. We were in extremely mild air of sub-Saharan origin which had invaded us all over the country, but also among our neighbors on the side of Belgium and Germany. And then there is an air mass which is of arctic origin and which descends directly to us in a northerly flow, "explains the meteorologist.

"This cold air will invade us from Monday, with a generalization of frosts for the next night."

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Last Wednesday was the hottest afternoon in March in seventy-five years (1947).

Even if it is traditional for March or April to have variations of this type, the thermal amplitude that we will experience, compared to the minimum expected this week, is not common.

A rare phenomenon on a national scale

"We will end up with a difference of almost 24-25 degrees, even if it is still to be refined. On a day and on a given geographical point, we can end up with even greater amplitudes - in particular the record in France around 35 degrees, with frosts near Mont de Marsan and an afternoon temperature that had reached 33 degrees. On the other hand, over the entire country, it is extremely rare to find such an amplitude! ", emphasizes Sébastien Leas. 

We have to go back to July 2019 during the enormous heat wave that France experienced, "with records that had also been broken in many places, especially in Paris. And then, four days later, we had minimum temperatures below the seasonal values. But we did not have the same feeling since we had gone from extremely stifling heat to much more breathable air ", recalls the forecaster, while this week we will rather go from fairly pleasant temperatures to freezing temperatures.