A new storm hit the region as rescuers started a new day of searching. Interior Minister Interior Minister Brice Hortefeux said he feared the toll would rise after what he called an "unprecedented catastrophe".
The worst storms since 1827 left a torrent of muddy brown water surging through the Provence town of Draguignan where 15 of the dead were found.
Scores of cars were piled on top of each other. Holiday homes and camp sites in the region were devastated.
"We are looking for people, we check that there is nothing under the remains of the cars," said the deputy prefect for Draguignan, Corinne Orzechowski. A special mortuary for the victims was set up in the town of 40,000 people.
The swollen Artuby river which goes through Draguinan also hit the village of Trans-en-Provence where five other bodies were found.
One victim was found at Luc, one at Roquebrune and one at Frejus on the Cote d'Azur and one in the Saint-Cassien lake. The floods also badly hit the stars' playground of St Tropez. About 25,000 homes were still without electricity on Thursday.
Helicopters were used Wednesday to rescue people trapped on roof tops and in cars. Emergency teams also moved 436 inmates to nearby jails from a flooded prison in Draguignan where the water covered the first two floors.
At the resort of Frejus, more than 1,500 people were taken to safety, many in inflatable boats or by helicopter.
About 2,000 soldiers, firefighters and police were brought in to lead the rescue operation after the floods swiftly rose.
The SNCF rail company halted train services along the coast between Toulon and Nice until Friday. Many smaller roads inland remained blocked.
President Nicolas Sarkozy will visit the area early next week, his office said. Sarkozy issued a statement expressing condolences for the victims' families.
Orzechowski said more than 30 centimetres (12 inches) of rain had fallen since Tuesday in Draguignan.
"We woke up to find a city that was devastated, extremely battered with overturned cars floating in the streets, collapsed roads and gutted houses," she said.
Flooding has also hit southwestern France, including the Atlantic resort of Saint-Jean-de-Luz.