September 2024 was the month of September “the wettest in 25 years” in France, with “nearly 60%” quantity of rain above normal, Météo France announced on Monday September 30.
In terms of temperatures, despite “feeling of freshness”the national average in September was “close to normal” of season, being only 0.4 ° C lower than the average for the period 1991-2020, added the meteorological observatory. September 2023 was the hottest ever measured in the country (+ 3.6°C above normal).
“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 on average in September 1999, according to the monthly climate bulletin.
Excess rainfall
“There is excess rainfall over almost the entire country” et “reaches even more than double the normal in New Aquitaine, in the Massif Central, the Paris Basin, the Channel coasts, as well as in the Northern Alps and in the north of Corsica”notes Météo France.
Orange rain-flood alerts have been triggered in Corsica, Seine-et-Marne and the Alps, among others.
At the beginning of September, the Aspe valley (Pyrénées-Atlantiques) was seriously affected by flooding while the Alpes-Maritimes suffered a Mediterranean episode pouring a month and a half of rain in 24 hours on towns like Fréjus or Mandelieu-la- Napoule.
“Very fresh feeling”
“Only the south of Brittany, Languedoc and Roussillon have a rainfall deficit”particularly marked 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, 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 cumulative rainfall reached “ 660 mm since January 2024, compared to 634 mm of average annual cumulation”, measured Météo France.
Despite a national average temperature 0.4°C below seasonal norms, Météo France is not announcing the end of a series of more than 2.5 years of monthly temperatures close to or above seasonal norms because “a month is considered to comply with seasonal norms when its average temperature is between -0.5°C and +0.5°C compared to the 1991-2020 reference values”explains the observatory.
1°C below seasonal values
“On the other hand, with an anomaly of 1°C below seasonal values, the maximum temperatures leave a very cool feeling”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 humanity.
