Météo-France places nine southwestern departments on orange storm alert

Atmospheric conditions and alert levels

A low-pressure system positioned between the north of the Azores and Portugal will move toward the Bay of Biscay, driving a widespread shift in weather across France on Monday, 24 August. The clash between cooler Atlantic air entering from the west and a surging warm air mass ahead of it will destabilise atmospheric conditions across large parts of the territory. In response, Météo-France issued orange thunderstorm alerts for nine departments situated across the South-West and the Massif Central. The initial orange warnings will take effect in Gers and Lot-et-Garonne at 14:00, expanding at 15:00 to Haute-Garonne, Tarn-et-Garonne, Lot, Dordogne, Corrèze, Tarn, and Aveyron. Additionally, 63 departments will remain under yellow warning, while Bouches-du-Rhône, Gard, Hérault, and Vaucluse carry specific yellow alerts for rain and flooding. La Chaîne Météo separately placed 15 departments under orange alert for severe storms.

On Monday, an Atlantic low-pressure system and its cooler air will approach the west of the country while a warm air mass rises ahead of it. This conflict of air masses will destabilise the atmosphere and encourage the development of thunderstorms from the southwest toward the north and east of the country.

Progression of the storm system

Initial atmospheric disturbances will form on Sunday afternoon with increasing cloud cover over the Pyrenees and the Massif Central. By Sunday evening, localized storm cells will gather over Aquitaine, bringing potential hail and easterly wind gusts reaching between 40 and 50 km/h across western France and Occitanie. On Monday morning, unsettled weather will bring scattered storm showers to the Atlantic coastline, Pays de la Loire, and northern Aquitaine, while the remainder of the country experiences calm conditions beneath hazy skies. By Monday afternoon, convective storm cells will consolidate into organised squall lines spanning Nouvelle-Aquitaine to the Massif Central, with severe activity centered over northern Occitanie, Auvergne, and eastern Aquitaine. The system will push eastward into Languedoc-Roussillon during Monday evening before expanding into Provence overnight, alongside secondary storm developments extending from the Centre region into Grand-Est.

Anticipated wind, rainfall, and hail hazards

The incoming storm cells will bring intense local precipitation, severe wind gusts, and hail to affected regions. Meteorological models project rainfall rates of 30 mm or more within a single hour in the heaviest downpours. Wind speeds will frequently register between 90 and 110 km/h along the path of the storm lines, with isolated gusts reaching up to 120 km/h. Intense electrical activity will accompany the frontal passage as the storm system crosses south-central France toward the Mediterranean coast. Météo-France stated that the orange alert perimeter could widen to encompass neighboring departments in southeastern France if the convective system intensifies during the night. Residents and travelers in the designated alert zones are advised to secure loose property, limit outdoor travel during peak hours, and stay updated through regional weather bulletins.