“Exceptional” nighttime heat levels recorded on Sunday, particularly in the South-West

Plus 26°C in Pau, 23.6°C in Biarritz, 23.4°C in Tarbes, 24.4°C in Orthez… Nighttime heat levels “exceptional” for the month of November were recorded during the night of Sunday 24 to Monday 25 November. Consequence of global warming and a Foehn effect, underlines Météo-France.

The night was “extremely mild across the whole country, and even more so in the South-West”explained Matthieu Sorel, climatologist for the meteorological organization, to Agence France-Presse. The phenomenon is explained by the presence of a “South wind everywhere”which brings “a great sweetness”, “accentuated by the Foehn effect” in the Pyrénées-Atlantiques, Landes and Hautes-Pyrénées, under the influence of the Pyrenean relief.

The Foehn effect, which can occur at any time of the year, occurs when the wind crosses a mountain barrier, and experiences a “significant warming of the air mass”. “This is what we observed last night, where the temperature reached 26.3°C in the middle of the night in Pau”explained Mr. Sorel.

“A marker of climate change”

The Foehn effect was also observed in Brittany during the weekend. “It was three degrees warmer on the north coast (…) only on the south coast, because this air mass was raised by the Armorican relief and then descended towards the Emerald Coast.where “nocturnal mildness records” were beaten locally for the period, with for example 15.6°C on the island of Bréhat.

Late Monday morning, the wind was picking up. “to tip and the foehn effect to stop”continued the climatologist, so that the temperature “is going downhill”with for example 14°C in Biarritz.

The temperatures observed last night reached “very, very high, very impressive levels” for the month of November, underlines the climatologist. “Air masses like that, for this time of year, are something we don’t see, without climate change”he explained, “We have temperatures well above normal everywhere”15°C in Lille, 16°C in Paris, 17°C in Besançon.

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”underlines Mathieu Sorel.