Posted on 06/19/2025 05:55

Reading time: 5min

The hexagon will experience an episode of high temperatures at the end of the week even before the start of the summer. An increasingly rare phenomenon due to global warming.

A thermometer climbing higher and higher and earlier in the year. A dry, sunny and hot weather gradually fell on France from Thursday, June 18. The threshold of very strong heat, at more than 35 ° C, should be reached in the west on Friday, according to Météo-France. And this very hot air could then win the northern regions during the weekend, leading to a probable heat wave in France. One less and less rare phenomenon from the end of spring.

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“We observe, in a very well documented way, that the heat waves are increasingly early, more and more and more intense”explains François Gourand, forecaster at Météo-France. A trend, linked to climate change, that can be visualized in the infographic below.

Between 1947 and 2024, Météo-France Has listed 49 heat waves, corresponding to an episode where temperatures are abnormally high for several days. Over the first ten years of this reference period, from 1947 to 1957, four heat waves were thus measured. This figure has multiplied by five over the last ten years, from 2014 to 2024.

Beyond their frequency which has accelerated, these waves of heat are also earlier … but also late. “A heat wave that would be triggered in mid-June, as it is likely at the end of the weekend, this would be part of this trend of early heat waves”confirms François Gourand. Ditto for those regularly observed after August 15 in recent years. In short, these high temperatures are no longer only reserved for two summer months, as was the case several decades ago.

“The extension of the summer heat period of several weeks is a marker of climate change.”

François Gourand, forecaster in Météo-France

in franceinfo

Finally, heat waves are also more intense. To measure this, Météo-France calculates the national thermal indicator, the average temperature of France. This index must exceed 25.3 ° C over a day as well as 23.4 ° C for at least three days so that the French forecastist considers that we are in a heat wave.

For heat waves, the definition depends on the regions. For example, in Toulouse, Météo-France will talk about heat wave when, for at least three days and three nights, the maximum temperatures exceed 36 ° C and the minimum temperatures are greater than 21 ° C.

These temperatures are often widely exceeded locally. This was notably the case during the heat wave of 2003, where temperatures above 40 ° C had been recorded in Toulouse, Lyon, Dax or Orange, recalls Météo-France. On the whole of France, this exceptional episode of heat of 16 days had reached maximum intensity of 29 ° C. In 2019, a shorter heat wave had reached even higher temperatures on average.

And it’s not over. With climate change, heat waves will continue to become more and more early, intense and long. In 2050, in a France at +2.7 ° C compared to the pre-industrial period, the number of days of heat waves will be multiplied by five, according to Météo-France. And by 10 in a France at +4 ° C, by 2100. They could also take place in mid-May and until the end of September.

Since the 19th century, the average temperature of the earth heated 1.1 ° C. Scientists have established with certainty that this increase is due to human activities, consumers of fossil fuels (coal, oil and gas). This warming, unprecedented by its speed, threatens the future of our societies and biodiversity. But solutions – renewable energies, sobriety, decrease in meat consumption – exist. Discover our answers to your questions on the climate crisis.