Warm and Dry September in France: Record Temperatures and Low Precipitation
September 2026 was recorded as the second warmest September ever in France, while also being the third driest since 1958. This double record raises questions about the underlying climate mechanisms and their impacts on agriculture and weather forecasting.
In September 2026, the national average temperature reached 21.3°C, making it the second warmest September ever recorded. Meanwhile, cumulative precipitation totaled only 23mm, making it the third driest September since records began in 1958, according to Météo-France.
A Record Month for Heat and Drought in Metropolitan France
The recorded temperature of 21.3°C was well above the historical average of 19.1°C for September, with highs exceeding 30°C in the southwest and southeast. Stations in Nîmes, Montpellier, and Perpignan recorded daily maxima above 33°C, while the northwest experienced temperatures above 24°C, far above seasonal norms. Precipitation was particularly scarce in the Grand West and Southeast regions, where monthly totals remained below 15mm, less than half the average of 48mm.
These anomalies were confirmed by Météo-France's automated station networks, which emphasize that the combination of heat and drought constitutes an alert signal for emergency services and farmers. The ECMWF outlook shows that medium-term forecast models had already indicated a trend towards higher temperatures, but the precipitation sequence was more severe than expected, increasing forecasting uncertainty.
Why September Was So Warm and Dry
The phenomenon can be explained by the persistence of subtropical high pressure that established itself over Western Europe from late August. This atmospheric blocking limited the arrival of moist frontal systems from the Atlantic, reducing rain opportunities. Meanwhile, weak winds facilitated warming of the near-surface atmospheric layer, amplifying daytime temperatures.
Satellite data from Copernicus showed a 12% decrease in cloud cover compared to the last decade's average, increasing direct solar radiation. Furthermore, neural network models like GraphCast, trained on decades of observations, have identified a strong correlation between high-pressure intensity and reduced precipitation in Mediterranean regions. This machine learning capability now enables quicker detection of prolonged drought episodes.
Detailed Scientific Analysis of the Blocking
High-pressure blocking acts as a 'persistent anticyclone' that prevents typical Atlantic perturbation dynamics from penetrating French territory. Dynamically, the pressure gradient stabilizes, limiting low-altitude convergence generation, which is essential for convective cloud formation.
