September 2024 was the rainiest month of the century, Météo-France announced. The readings also indicated temperatures “close” to seasonal norms.
A rainy return to school. September 2024 was the “wetterest September in 25 years” in France, with “nearly 60%” of the amount of rain above normal, Météo-France announced this Monday. These historic levels in France are part of a torrential month of September across the world, marked in particular by deadly floods in the Sahel and Europe and Hurricane Helene in North America, phenomena reinforced by the effect of climate change of human origin.
“With a rainfall excess of almost 60% compared to 1991-2020 normals (119 mm), September 2024 becomes the wettest month of September in 25 years”, behind the 130 mm recorded in September 1999, specifies the climate bulletin monthly from Météo-France. “The rainfall is excess over almost the entire country” and “even reaches 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 in the north of Corsica,” noted the national agency, sometimes leading to the triggering of orange rain-flood alerts.
At the beginning of September, the Aspe valley (Pyrénées-Atlantique) experienced destructive floods, while the Alpes-Maritimes suffered a Mediterranean episode with a month and a half of rain in twenty-four hours in towns like Fréjus or Mandelieu- la-Napoule. “Only the south of Brittany, Languedoc and Roussillon have a rainfall deficit”, particularly marked in the Pyrénées-Orientales (-30%), which has been experiencing a very serious lack of rainfall for more than two years.
For a large part of the territory, this excess rain has been a constant since January, with average annual totals already exceeded in nine months in Nice, Saint-Nazaire, Strasbourg and even Le Mans and in the capital. In Paris, the total rainfall has reached “660 mm since January 2024, compared to 634 mm of average annual total”, measured Météo-France. In connection with the rains, “there was a deficit of sunshine in the country (-20%)”, notes the public observatory, according to which the sun only shone more than normal in January and August.
Temperatures “close” to seasonal norms
On the temperature side, despite a “very cool feeling”, the average in France in September was “close to normal”, because only 0.4° C lower than the reference for the period 1991-2020, added the observatory meteorological, which considers “conforming to normal” the months between -0.5° C and +0.5° C. “Over the last six years (2018 to 2023), each month of September displayed an average temperature at above normal”, underlines Météo-France, which explains the evolution of the common perception of so-called “seasonal” temperatures.
September 2023 had even set a new heat record, with a national thermal indicator (average over 30 reference stations) measured 3.6° C above the 1991-2020 normal, itself already significantly warmer than in beginning of the century. We have to go back to January 2022 (-0.5° C), more than two and a half years ago, to find in France a month considered colder than normal, established on the average of the last three decades. The country, however, experienced “two episodes of coolness, in the middle and at the very end of the month” which left their mark, with maximum temperatures up to 5° C lower than normal, “worthy of a month of October “.
Considering only the daily maximums, the September measurements “leave a very fresh feeling,” recognized Météo-France. “The temperature in Toulouse reached the threshold of 25° C only 3 times in September 2024, compared to 27 times in September 2023,” the bulletin reported.
On September 29, monthly cold records were broken at dawn “thanks to a very occasional cool spell”, with 1° C in Amiens (Aisne) or 2.5° C in Carcassonne (Aude). . “Cold records are not incompatible with climate change” but “they are becoming more and more rare”, recalled Météo-France.
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