This July 18 will undoubtedly remain engraved in the memory of the Bretons.
At 5 p.m., Brest had crossed the 39°C mark while Lanmeur recorded more than 40°C and Saint-Brieuc 39.5°C.
Unheard of in the region.
Many other cities in the West also experienced unprecedented temperatures, including Nantes (42°C), Angers (40.7°C), Saintes (42.4°C), Niort (41°C) or still Cazaux (42.4°C) and Biscarrosse (42.6°C).
“The temperature record in Brest, which has held since 1949 with a temperature of 35.2°C, has been greatly exceeded
,
by several degrees, which is very rare”,
recalls Pascal Scaniver, forecaster for La Chaîne Météo (1 ).
Nationally, however, this July 18 should not ultimately dethrone the days of August 5, 2003 and July 25, 2019, for which the "average thermal index" had peaked at 29.4 ° C.
“This index is calculated by taking the average of the minimum and maximum temperatures of a day, recorded in 30 weather stations representative of the country”,
recalls Pascal Scaniver.
“However, unlike the heat waves of 2003 and 2019, the minimum temperatures remained on the whole rather low, and the thermal index should rather be between 28.5 ° C and 29 ° C.”
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Above all, this "heat apocalypse", according to the term chosen by Météo-France, is circumscribed in space and time.
The temperature peak therefore does not occur everywhere in the country at the same time.
France is indeed swept from west to east by a depression coming from Morocco, via Portugal and Spain, which moves masses of extremely hot air.
“Once the depression passes, temperatures should drop by 10°C, even 20°C, sometimes quite quickly”,
explains Pascal Scaniver.
On the west facade, this brutal cooling will begin to be felt this Tuesday morning.
Brittany and the Pays de la Loire should thus find temperatures between 21 ° C and 26 ° C on Tuesday, the same as those forecast the previous night!
At the same time, Île-de-France, Hauts-de-France and the east of the country will in turn experience temperatures between 38°C and 40°C on Tuesday, as the air mass hot is sweeping over these regions.
“But, from Wednesday, it will already be more breathable in these regions, with temperatures close to 30 ° C,
estimates Claire Chanal, forecaster at Météo-France.
The heat wave will therefore be over on Wednesday, but the heat wave will persist in the country without it being possible to predict when it will end.
In particular, it will continue to be hot in the southwestern quarter with temperatures up to 36°C locally.
Occitanie, like the lower Rhône valley, has already recorded 7 days at over 35°C and could break the record for the number of consecutive days of very hot weather.
Forecasters see no improvement in the near term.
The heat could stagnate for several more days in these territories with peaks at 40°C.
France is not alone in facing very high temperatures in July.
Spain is coming out of a state of alert and has recorded peaks of 45°C.
More unusual, the United Kingdom is for the first time in its history placed on red alert "extreme heat" and was preparing Monday to exceed 40 ° C in several regions of the kingdom.
Exceptional situations that risk becoming the norm in the years to come, warn climatologists.
"The increase in frequency, duration and intensity of these (heat waves) events in recent decades is clearly linked to the observed warming of the planet and can be attributed to human activity",
confirmed the World Weather Organization on Monday, in a commentary on the extreme heat experienced by Western Europe.
(1) Property of the Figaro Group.
