The deaths included two women, aged 86 and 26, who were found drowned in a cellar in the Bouches-du-Rhône region. Corsica was also hit by severe weather, with local media reporting that a 4x4 vehicle was swept away by floodwaters; one occupant escaped through a window but another man was found dead. Authorities have not released details of the fourth death.
In the towns of Mouriès and Saint-Martin-de-Crau, between Montpellier and Marseille, dozens of residents were accommodated in emergency shelters after the floods. Officials said one person had been injured in that area. Transport Minister Philippe Tabarot wrote on X that roads and train lines had been disrupted.
"The water has risen to unprecedented levels," Jacques Witkowski, prefect of the Bouches-du-Rhône department, said in a statement on Wednesday. He expressed "a thought for all those who are in distress", adding: "We are mobilised at an exceptional level to resolve several issues."
More severe weather is forecast, with Storm Austen, a newly named system moving in from the Atlantic, expected to reach France's north-west. Météo-France has issued an orange-level wind warning for five western departments from Thursday evening into Friday: Côtes-d'Armor, Finistère, Morbihan, Ille-et-Vilaine and Manche.
Storm Adam had already brought severe flooding to eastern Spain, where at least three people were killed. Several towns along the Mediterranean coast were cut off by floodwaters and helicopters were deployed to rescue people stranded on rooftops. The Military Emergencies Unit found the body of a woman in the town of Oliva, Valencia, during rescue operations on Monday. Two other women were confirmed dead over the weekend: one washed up on a beach in Sagunto, in Valencia, and another swept away in Cabrera de Mar, near Barcelona.
Spanish Prime Minister Pedro Sánchez promised national government resources to help reconstruction during a visit to the Valencia region on Tuesday. The Valencian government approved an aid package of €23.5m (£20m) for those affected by Storm Adam.