Why is the heat peak that hits France this Friday different from previous heatwaves?

Shorter days, lower sun, fewer impacted regions… Until Monday 7th September 2026, however, part of France will suffocate under extreme temperatures.

Unsurprisingly, summer 2026, marked by heatwaves, droughts and fires giants, was “the hottest” ever recorded in France, the Minister of the Transition announced this Thursday 3rd September 2026 ecological, Monique Barbut.

The number of times during this summer when Météo France stations exceeded 40°C a significantly increased this year compared to a classic summer. And, while autumn (meteorological) started on September 1, 2026, a new heat peak is expected this weekend in a southern part of France. It will end this Tuesday 8th September 2026, with the arrival of a disturbance which promises to be very rainy in places. “But this heatwave episode would be a little different from the previous ones”, underlines, meteorologist Yann Amice.

A national thermal indicator well below the 30°C at the end of June

First of all, the ITN, the national thermal indicator, should be around 24°C this Sunday, September 6, 2026, at the peak, far from the 30°C of the historic heatwave at the end of June 2026.

As a reminder, the ITN is the average air temperature measured across the country (average of minimum and maximum temperatures over 24 hours on 30 weather stations distributed in a balanced manner in France). On this basis, across France, Wednesday 24th June 2026 was the hottest day on record since 1947, reaching 30°C for the first time, therefore, on a 24-hour average of daytime temperatures and of the night, tied with the following day, Thursday 25th June, and ahead of the 29.9°C of Tuesday June 23, 2026. These three days exceeded the absolute record of 29.4°C of July 25th, 2019 and August 5, 2003.

For comparison, also, the day of the 13th August 2026 was the hottest of this last heatwave episode on a national scale, with 28.8°C on average over 24 hours… A difference of 4°C, therefore, with what awaits France in the coming days.

In September, the sun is lower and the days are shorter

Another parameter, the sun. In September, the sun is lower and the days are shorter, therefore the nights longer. As a result, the light energy received is less.

Another particularity of this late heat peak is that it will mainly affect the south of the country. The fact remains that this Friday 4th September and this weekend, temperatures of 36 to 40°C are expected in the south of Aquitaine, Occitanie and the Rhône valley a heat that will often be unprecedented for the month of September in these regions with undoubtedly many monthly records broken, again, as in previous months. Météo France has also triggered the orange heatwave alert. The only time this has been the case so far was in September 2023.

This weekend of Saturday 5th September and Sunday 6th September, while the south will still be crumbling under extreme temperatures –with possible 40°C between Occitanie, Lyonnais and Provence –, the regions of the northern half should experience a mercury between 23°C and 30°C generally, and even a little less close to the Channel thanks to a very present maritime component. Even if on Sunday 6th September, the southeast flow will bring warm air up even to the northern half, but to a lesser extent than in previous episodes. And above all, it won’t last.

An episode of extreme heat which will end at the beginning of next week

And this heatwave in the south will not last. The last heat wave lasted from the 28th July to the 19th August. Lasting 23 days, it had thus equaled the longest heat wave ever recorded, namely that of July 1983, while displaying a greater intensity.

Temperatures should begin to drop next Monday evening and especially between Tuesday 8th September and Wednesday 9th September with the return of both rain, sometimes intense, but also a northwest wind which will therefore lower the mercury quite spectacularly.

While it is not uncommon to observe late heat episodes in September, they are made more likely and more intense with the climate change, remind the scientists.

The last notable late heat episode was in September 2023 (September 3rd-11th, 2023). This weekend’s episode should be less extensive geographically, therefore, but more intense in the southern half of the country where monthly maximum temperature records are expected between Friday and Sunday.

Bodies will still be put to the test

A different episode on a national scale, but just as trying for the inhabitants of the South who will still experience extreme temperatures after this record-breaking summer…

And the appearance of sanitary effects linked to heat is not limited to extreme phenomena: it is observed as soon as a heat peak occurs corresponding to the level of yellow meteorological vigilance, insists Météo-France.

When exposed to heat, the human body activates thermoregulation mechanisms that allow it to compensate for the increase in temperature (sweating, increased blood flow to the skin through dilation of skin vessels, etc.). When these mechanisms are overwhelmed, pathologies linked to exposure to heat appear: headaches, nausea, sunstroke, muscle cramps, dehydration. The most serious risk is heat stroke, which can lead to death.

During hot weather, protect yourself!