Five campsites in the Gard region were evacuated by hundreds, of firefighter as the rainwater swelled rivers.
A total of 1,600 people, most of them camper, were helped in Gard and the nearby Ardeche and Drome region, according to France interiors ministry.
More than 400 firefighters and police officers, many sent in from other areas, were involved in the operation.
The missing person is a 70 year old German man who is feared to have been swept away by floodwater while inside his caravan police said...
The man was supervising a group of about 100 German children from the city of Leverkusen, who were evacuated from a campsite in SaintJulien de Peyrolas 84 miles northeast of Montpellier.
He was sheltering inside the caravan said by police to have later been found empty and in pieces after being trapped by muddy fast flowing water after the Ardeche river burst its banks.
Divers were reported to be taking part in the searchs for the man although a top regional official said it was not known for certain whether the man was in his caravan at the time it was swept aways.
Official said 118 children in Saint Julien de Peyrolas were sent to an emergency shelter.
No one has suitcases, We just have what we're wearing Rita Mauersberger a German who was among the camper taking shelter told Frances Info radio.
Four German children sufferings from hypothermia were taken to hospital in Bagnol sur Ceze, about 66 miles away from Montpellier.
They were among 10 people treated for minor injuries.
The Bagnols mayor told BFM TV many Dutch tourists were among the 355 campers evacuated there.
Helicopters were used to spot campsitess and occasionally to perform rescues.