Less than a month after the previous heat wave, France is entering a new heat wave. An episode that will again be intense, but probably longer, and in the regions already most affected in June.
“One of the hottest episodes ever, if not the hottest”
“We are clearly on a longer episode, much longer, and undoubtedly one of the hottest ever recorded in France, as in July 2019 and August 2003”, details Matthieu Chevallier, from Météo France.
From the point of view of temperatures, “we should be at the level of those recorded last June”, he explains. But “areas of uncertainty” raise fears of possibly higher levels.
Seven departments are already on orange alert. A number that should quickly change as the heat wave extends.
> Map: what are the vigilance thresholds in your department?
For the time being, the temperatures recorded are already, this Wednesday, around 35 to 38 degrees, in the south-west and the lower Rhône valley. It’s over 30 degrees almost everywhere else.
Monday July 18, 2022, new hottest day?
This Thursday, temperatures will rise further, to reach or even exceed “locally more than 40°C”, before a very small drop on Friday – despite new peaks at 40°C.
But it is Saturday that the episode will start to rise again throughout the country, with “a gradual warming of the air mass by high pressures, amplified by a cold drop phenomenon off Portugal, which will promote a upwelling of very hot air from Morocco this weekend”, specifies Météo France.
Saturday’s heat will therefore increase further on Sunday, and reach its peak “probably Monday, which could become the hottest day ever known in France”. So far, the record in this area dates back to August 2003 and July 2019, with an average temperature across the country of 29.4°C. This temperature is an average over 24 hours: it may seem “low”, but it includes day and night temperatures!
In terms of peaks, several monthly temperature records should be broken, even absolute records.
Seven to ten days, and after?
Currently, most departmental records in France exceed 40°C. Some even “fell” last June, when we had never reached 40 in June before:
> Map: what is the absolute temperature record in your department?
At best, a cooling could start at the earliest this Monday evening from the west, but this is still part of the uncertainties. If this is the case, the heat would begin to shift to the east of the country, where the heat wave would persist. But for now, nothing is less certain.
The end of the episode is not yet predictable
Claire Chanal, forecaster at Météo France
Indeed, “we are talking about a heat wave of seven to ten days, but here we are at the limit: we cannot yet say if the episode will end at that time”, explains Claire Chanal, forecaster at Meteo France. “It is not excluded that the very hot weather will continue beyond,” she adds, at least in the south-west of the country.
More frequent heat waves, records falling more often
In the longer term, Météo France recalls that this episode is the 45th to occur in France since 1947, and that they are more frequent: most have occurred in the last thirty years, even if 1947 remains a significant year. The strongest since have occurred in 1983, 2003, 2016, 2018 and 2019. Most current temperature records are less than 20 years old, depending on the department.
> Map: when is the absolute temperature record in your department?
This type of event is however considered extremely rare in a climate “unmodified by human activities”, recalls climatologist Matthieu Sorel. On the other hand, he specifies, the number of hot days will be multiplied by 3 to 4 if greenhouse gas emissions are limited, and by 5 to 10 with high emissions. Currently, even by strongly limiting greenhouse gases, it should double. And this type of episode shows temperatures “5°C above last century levels”, on average.