what is the “polar air shift” which will cause temperatures to drop in France from Monday?

While mainland France has been enjoying the sun for several days, the end of spring has some surprises in store. After the storms forecast for Sunday June 9 in the south of the country, the cool weather will persist until the middle of next week over a large part of the territory due to a “polar air stall”, Frédéric Long, forecaster at Météo-France, explains to franceinfo.

What is this phenomenon? The weather in France is determined in particular by the jet stream, a tube of winds present at altitude, which oscillates between masses of warm air, coming from the south, and masses of cold air, coming from the north. Usually, at this season, the oscillations caused by the meeting between cold and warm air tend to send the cool air towards the north of Europe.

But it happens that the oscillations become distorted, due to the general meteorological context. Result: the cold air coming from Iceland or Greenland will this time be propelled to our latitudes.

Not too much to worry about, though. “As we go back south, this polar cold will warm up” to become fresh, emphasizes Frédéric Long. It will therefore not be necessary to take your down jacket out of the closet: the maximum temperatures should on average be “3°C to 4°C” below reference normals on Tuesday and Wednesday, according to the forecaster. That is, at the hottest of the day, around 19°C or 20°C on average in the northern half, and 22°C in the southern half. Temperatures will begin to rise on Thursday, with “nice day expected in most regions”. However, the weather will be overcast from Friday due to a southwesterly flow, warns Frédéric Long.

This phenomenon of polar air stalling, which is not linked to the rainy episodes of recent weeks, is quite common, according to the forecaster. “In recent years, due to climate change, we are less accustomed to cool temperatures in summer. But it remains possible.” The arrival of this mass of fresh air in the coming days does not, however, determine the weather in the coming months, the meteorologist points out. The hypothesis of a summer hotter than seasonal norms remains the hypothesis favored by Météo-France.