France experienced its rainiest month of September in 25 years

With a rainfall excess of almost 60% compared to 1991-2020 normals, “September 2024 becomes the wettest month of September in 25 years”, behind the 130 mm recorded on average in September 1999, Météo-France calculated.

The start of the school year had not been so rainy in France since the turn of the last century. With cumulative rainfall calculated at 119 mm on average over the territory, i.e. “nearly 60%” above normal, September 2024 was the month of September “the wettest in 25 years” in France, announced the forecaster, Monday September 30, in his monthly climate bulletin. This month is behind September 1999, which then received an average of 130 mm of precipitation. “There is excess rainfall over almost the entire country” And “even reached more than double the normal in New Aquitaine, on the Massif Central, the Paris Basin, the Channel coasts, as well as on the Northern Alps and the north of Corsica”, Météo-France note.

During the month, orange rain-flood alerts were triggered, among others, in Corsica, Seine-et-Marne and even in the Alps. At the beginning of September, the Aspe valley (Pyrénées-Atlantiques) suffered significant flooding, while the Alpes-Maritimes experienced a Mediterranean episode pouring a month and a half of rain in 24 hours on towns like Fréjus or Mandelieu-la -Napoule. Rainy episodes sometimes marked by floods and destructive landslides.

“Only the south of Brittany, Languedoc and Roussillon have a rainfall deficit” in this month of September, a particularly marked situation in the Pyrénées-Orientales (-30%), with a very serious precipitation deficit for more than two years.

For a large part of the territory, this excess rain has been a constant since the start of the year. In several cities, such as Nice (Alpes-Maritimes), Saint-Nazaire (Loire-Atlantique), Strasbourg (Bas-Rhin), Le Mans (Sarthe) and Paris, the cumulative rainfall recorded in nine months already exceeds average annual accumulations.

In terms of temperatures, the national average in September wasé “close to normal” of season, 0.4°C lower than the average for the period 1991-2020. If Météo-France mentions “a feeling of freshness”, the latter could result from an impressive contrast with September 2023, the hottest ever measured in the country (+3.6°C above normal), recalls the organization in its monthly report.

“With an anomaly of 1°C below seasonal values, the maximum temperatures leave a very cool feeling,” he explains, especially since the country has experienced “two episodes of freshness, in the middle and at the very end of the month”.

“Over the past six years (2018 to 2023), every September had an average temperature above seasonal norms“, recalls Météo-France, illustrating the effects of global warming in France caused by greenhouse gases emitted by human activities. However, “a degree of warming leads to 7% more humidity in the atmosphere”explained Christophe Cassou, climatologist and research director at CNRS, on Tuesday.

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