Hot temperatures are returning to France this Monday (September 12), but are expected to be followed by significant storm activity from Wednesday.
Temperatures are predicted to sit around 35C in the south-west – with the possibility of localised spikes to 38C – and between 25C and 30C across everywhere but the very north-east of France.
The hot weather is due to the former hurricane Danielle which is causing a weather depression and later a ‘heat pump’ over France.
What can be expected today?
Pic de fortes #chaleurs :— Météo-France (@meteofrance) September 11, 2022
Températures remarquablement élevées pour une deuxième décade de septembre dès ce dimanche, et surtout demain #lundi sur le #sudouest.
⚠️⛈ Chaleur de courte durée.
Dégradation orageuse à partir de mardi en particulier sur le sud du pays. pic.twitter.com/19kkEfcOyG
Temperatures will peak this afternoon, with Gironde and Landes being most likely to see highs of up to 38C. This could represent a record for this time of year.
In the north of Nouvelle-Aquitaine, Pays de la Loire and the west of Occitanie, people should expect temperatures of 30-35C, while in much of the rest of the country they will settle between 25C and 30C.
Only in northern areas of Grand Est should temperatures stay below 25C.
The heat will not last long, but is forecast to linger over the Mediterranean, with “disastrous consequences for ecosystems,” climatologist Christophe Cassou tweeted.
Sur ce diagnostic de rang, on voit bien se développer la #PlumeDeChaleur & son évacuation rapide de la , mais aussi sa persistance sur le bassin Ouest Méditerranée, contribuant à maintenir la #VagueDeChaleurMarine aux conséquences désastreuses sur les écosystèmes.— Christophe Cassou (@cassouman40) September 10, 2022
On land, storms will almost definitely arrive on Wednesday and even earlier in some places.
There are already yellow storm alerts in place in Charente-Maritime, Gironde, Landes, Pyrénées-Atlantiques and Hautes-Pyrénées today.
Gironde, Landes and Pyrénées-Atlantiques are also under a yellow heatwave warning.
Yellow weather alerts do not require residents to take any particular precautions but rather to remain aware of the evolving situation.
This unsettled weather is forecast to affect the Mediterranean coastline, Brittany, Ile-de-France and Alsace in particular.
As the week wears on, temperatures will return to seasonal norms, beginning on Wednesday or Thursday in the north and at the weekend in the south.
By the end of the week, afternoon highs will reach around 19C in northern regions.
Will there be a lot of rain?
Forecasters cannot yet offer a specific prediction on the amount of rainfall expected this week, but “atmospheric circulation will really favour very heavy rainfall,” Ms Cassou said.
Météo France has therefore put out a warning about the potential for “intense” rainfall and potentially “violent” storms, especially along the Mediterranean, in Hérault, Gard, Ardèche, Bouches-du-Rhône and Vaucluse.
Why is this happening?
This week’s hot spell is “quite typical, with an air depression which gets stuck to the west of the country off the French and Spanish coastlines, bringing a flow of hot air from the south,” Météo France meteorologist Florian Hortala told Franceinfo.
This particular depression has been caused by the ex-hurricane Danielle, which has come across the Atlantic.
“Before the 2000s, the temperatures wouldn’t have risen so high; climate change is giving us records. Finding ourselves under air masses creating temperatures of 36C, 37C or 38C is not normal,” Mr Hortala added.
The storms which will follow the heat are also partly due to the conditions created by rising global temperatures.
“A warmer climate increases the movement of moisture in weather systems, which intensifies wet weather events,” Mr Cassou said.
La particularité de cette #PlumeDeChaleur vient de son lien avec la dynamique tropicale car la petite dépression au large de la péninsule ibérique qui la génère correspond à l'ex-cyclone #Danielle qui a opéré sa transition tropique-extratropique https://t.co/3yykRfGdb8— Christophe Cassou (@cassouman40) September 10, 2022
Saharan sand travels to France again
As this week’s heat flows up towards France from the south, so will a cloud of dust from the Sahara Desert, which may be visible in the country today and tomorrow (September 13).
If you are not prevented from washing your car by drought restrictions and are thinking of doing so today, you may do better to wait until the sand has settled.