National weather agency Météo France has issued orange alerts for eight departments, seven of which are in the south of France.
The agency predicted floods, violent winds, and stormy weather.
It issued orange alerts for storms in the southern departments of Aude, Aveyron, Haute-Garonne, Hérault, and Tarn.
Winds are expected to reach up to 120km/hr in some areas.
The agency also issued orange alerts for floods in Gard and Bouches-du-Rhône – and further north in Saône-et-Loire.
The storm and flooding alerts are in place until at least Thursday morning, with another bulletin expected later on Wednesday.
An orange alert is the second highest warning level the agency issues, and urges the public to be “very vigilant”.
Residents have been warned to beware of falling trees, to keep off roofs, and to avoid secondary roadways.
The agency warned that residents could expect “significant damage” from the storms, which may affect electricity and telephone networks.
It advised residents to avoid using the telephone and electrical appliances.