The difference is impressive. While a large part of the north and northeast of the country fell asleep in cold and icy conditions on Saturday evening, these same departments woke up to much higher temperatures on Sunday morning. These, for example, went from -3.6°C on Saturday at 7 a.m. to 11.1°C at the same time this Sunday in Paris, from -5.9°C to 10.7°C in Nevers (Nièvre ) or even from -23.4°C to 7.1°C in Pierrefontaine-les-Varans (Doubs) at the same times, according to La Chaîne Météo.
According to reports from meteorologist Guillaume Séchet, the mercury rose 8°C in Paris between 1:15 a.m. and 3:40 a.m. on the night of Saturday to Sunday. “What is rare is above all the speed at which the warm weather took place,” observes the founder of Météo-Cities to Le Parisien. It's not so much that it was very cold yesterday (SATURDAY). »
How can we explain this sudden change in temperatures? “A flow of warm air rose from the south and quickly replaced the cold air” present in the north of the country, explains Gilles Matricon, forecaster at La Chaîne Météo. Concretely, the “fairly thin film of cold air” which covered the “northern half of France” was swept away by this “powerful southwest current coming directly from the Canaries”, adds Guillaume Séchet. This one, “quite powerful”, was “propelled” towards the north by a depression coming from the South-West.
This air mass replacement was facilitated by the thinness of the film of cold air, especially present on the ground, affecting the northern half. “As cold air is heavier than warm air, it tends to stay at ground level. But the temperatures were already higher at altitude,” explains Guillaume Séchet. “We therefore went from everything to everything: from very cold weather to almost exceptional mildness,” he adds. This also explains why it snowed little or not on Saturday evening. “It was freezing rain because the rain fell on cold ground, otherwise there would have been snow,” this specialist also points out.
However, this mild spell will not last for the rest of the week. “France will be affected by a new disturbance which will be accompanied by rain and storms, particularly in the Cévennes,” anticipates Gilles Matricon. “This Monday, a disturbance will gradually come from the Atlantic with a wind that will move towards the north,” he continues. This explains why temperatures will generally be higher this Monday morning than in the afternoon in the north and north-east of France (11°C in Paris Monday morning compared to 9°C in the afternoon , according to Météo France).
And after? “Temperatures will continue to drop next Tuesday and Wednesday,” notes meteorologist Guillaume Séchet. Météo France, for example, anticipates 4°C for Tuesday morning in Paris, Lille (North) and Strasbourg (Bas-Rhin). “We also expect snow in the plains between Wednesday and Thursday,” adds Gilles Matricon. At the heart of a most hectic week.
