“Exceptional” nighttime heat levels for the month of November were recorded during the night from Sunday to Monday, the result of a hot air mass such as global warming increasingly brings, and a significant Foehn effect.
Early risers had a strange surprise when they set foot outside on Monday, November 25. After a particularly hot day on Sunday for the season in certain regions, “the softness was also exceptional last night”confirms Christelle Robert, forecaster at Météo-France. At 6 a.m., it was around 25°C in Pau (Pyrénées-Atlantiques), while the stations of Dax (Landes) and Biarritz (Pyrénées-Atlantiques) showed 20.9°C and 20.1°C in the early morning. In the Paris region, Orly (Val-de-Marne) and Roissy (Val-d'Oise), also experienced summer night temperatures, with 15.1°C and 15.6°C, while Poitiers (Vienne) woke up with 15.5°C on the clock, according to Météo-France.
If, usually, it is at the end of the night that we observe the minimum temperatures for a given date, the opposite happened on Monday, while values began to gradually plummet with the arrival in the early morning in France “from the cold front of the disturbance associated with Depression Bert”.
Despite this nocturnal sweetness “exceptional, particularly from the South-West to the center and up to Ile-de-France”, continues the forecaster, “we cannot talk about records for the highest minimum temperature [pour un 24 novembre] since Météo-France is based on temperatures recorded between 6 p.m. the day before and 6 p.m. on the day.” And “the air mass remained mild and counteracted the natural cooling that occurs during the night”, explains Christelle Robert“the temperature then dropped with the change in air mass.” CThis is how Pau went from nearly 25°C around 6 a.m. to 15°C a few hours later, she continues.
On the other hand, the day before, the Campistrous station (Hautes-Pyrénées) largely beat its record for the highest minimum temperature for November 24. “After a very hot first night from Saturday to Sunday, temperatures remained high on Sunday during the day. We therefore observed a minimum temperature of 15.1°C, compared to 13.3°C for the previous record of November 23, 2014 “, explains Chistelle Robert.
“Air masses like that, for this time of year, are something we don’t see without climate change,” notes his colleague from Météo-France, climatologist Matthieu Sorel, cited by AFP. Globally, “we have small cold anomalies”, as illustrated by the recent early winter episode, with significant snowfall in the northern half of France last Thursday, and “very large warm anomalies”. “It is indeed a marker of the climate change in which we are experiencing”, he emphasizes.
It is in any case no coincidence that the hottest night temperatures were recorded in the Pyrénées-Atlantiques, Landes and Hautes-Pyrénées. Pointing “the Foehn effect”, Christelle Robert explains: “This is what happens when you have a strong south-oriented wind that meets a mountain. The flow passes over it and warms up as it descends on the other side.” A common foehn effect, but here “phenomenal”, points out another meteorologist on the Bluesky social network.
Phenomenal foehn effect this morning over the west of the #Pyrenees. At 06h UTC it was precisely 24.6°C at the Pau Uzein station. Since the recording of tri-hourly synoptic temperatures in 1945, this is the 5th highest temperature observed at 06:00 UTC in all months combined. 1/5
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— Gaétan Heymes (@gaetanheymes.bsky.social) November 25, 2024 at 8:26 a.m.
“These repeated southerly flows are now becoming the dominant flows of our winters, only opposed by a few westerly passages,” noted on Sunday on X the Météo Pyrénées account, citing “an assertion that must be correlated with our observations over the last ten years, and in particular since 2020/21”.
The Foehn effect has also been observed in Brittany, where “nocturnal mildness records” were beaten locally for the period, with for example 15.6°C on the island of Bréhat, according to Matthieu Sorel, cited by AFP. “It was 3°C warmer on the north coast (…) than on the south coast, because this air mass was lifted by the Armorican relief and then came down towards the Emerald Coast “he explains.
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