About 300 people were winched to safety, mostly in the northern part of Montpellier where several square kilometres were flooded.
Cars were lifted sometimes several hundred metres and some were found in trees or smashed against walls.
By mid morning on Tuesday, around thirty roads were still blocked and the Mosson stadium in Montpellier had water reaching up to the fifth row of seats.
Elsewhere in the south of France there were storms but less damage. A residence in the Pradet area of Toulon was evacuated and thirty people were led to safety.