In one hour, this early Saturday evening, the south-west of France will be delivered from the heat wave. The inhabitants of Pyrénées-Atlantiques and Landes owe this sudden cooling to a powerful wind coming from the West, called the galerne, indicates meteorologist Guillaume Séchet. In these two departments, the temperature will suddenly drop by almost 20 ° C in places, while they were affected by high heat like two thirds of the country placed in orange or red vigilance.
A little earlier, this wind has already cooled Santander, in Spain, where it was no more than 20 ° C on Saturday afternoon.
Known in the west of France, in particular on the Basque coasts, this meteorological phenomenon takes different names depending on the region: “brouillarta” in the Basque Country, “gwalarn” in Brittany, lists Ouest-France. Whatever its name, whose origin is Spanish, it is a sudden wind (temperature drop in about twenty minutes), cold and wet. The galerne, meteorological name used by Météo France, is a phenomenon “characteristic of the south-east of the Bay of Biscay”.
Biarritz will lose 20°C in one hour
It is characterized in particular by a sudden drop in temperature (from 12 to 15°C), a rapid rise in humidity (towards 85 or even 90%) and a “violent” rotation of the wind associated with a “sudden increase” in its speed, all “almost simultaneously and in a few minutes”. The phenomenon is spreading from West to East, specifies the institute of meteorological forecasting.
“In some cases, galern may be accompanied by precipitation. It suddenly interrupts a period of calm weather, generally sunny and warm. “The galerne arises most of the time between May and October, “three to four times a year on average (always in Biarritz), for a duration most often between one and three hours, the wind generally remaining in the West. »
Thus, the cities of Pau and Tarbes, which saw the thermometer climb to 40 ° C in the afternoon, will drop to 31 ° C in the evening then 20 ° C at night, indicates Franceinfo. In Biarritz, the temperature will drop from 42.9°C to 23°C, and it will drop by 10°C in Saint-Jean-de-Luz (from 38°C to 27°C).