Some 1,600 people, many of them children, were evacuated, and a 70-year-old German man helping to supervise youngsters at a summer camp in Saint-Julien-de-Peyrolas in the Gard region was feared to have been swept away by floodwater, along with his van.
Nearly 120 children were evacuated from the site as emergency teams helped around 750 people to safety across the Gard area.
Kathryn Alford, 44, from Welwyn Garden City in Hertfordshire, was at Huttopia Camping Le Moulin in Saint Martin d’Ardeche with her husband and two children.
She said severe storms started at around 7am on Thursday with very heavy rain and constant thunder and lightning.
«I looked out at one point and realised that the water level seemed higher than just massive puddles. Our neighbour’s bottom step had disappeared and things were floating past,» she said, adding that they had lost electricity.
Between storms, Ms Alford took pictures of people in canoes in the flood outside the mobile home she was staying in.
«I was quite frightened at first as I hate storms. Some people were concerned, but the campsite were good at reassuring us.
«I felt really sorry for the people whose tents were flooded,» she said.
It comes as French interior minister Gérard Collomb urged citizens and holidaymakers to show increased vigilance as potentially deadly flash floods hit several departments in southern France on Thursday.
Thousands of people have been evacuated from flooded campsites and two people have been reported missing since a heatwave gave way to heavy storms earlier this week.
Mr Collomb tweeted: “Intense thunderstorms are currently sweeping across the country. I call on everyone to exercise great caution. Local prefecture officials and safety and rescue services are fully mobilised.”
The severe storms which triggered the floods follow a prolonged spell of unusually hot weather that has blanketed France and large swaths of Europe.
The worst-hit areas are the southern departments of Gard, Ardeche and Drome, where more than 1,600 people – mostly campers – have been evacuated, local officials said. More than 400 firefighters and police, as well as four helicopters, have been deployed.
Two people were feared dead or missing on Thursday afternoon, according to French media reports.
A 75-year-old German man who was helping to supervise a group of around 100 children from a campsite in Saint-Julien-de-Peyrolas in the Gard region is thought to have been swept away by floodwater, regional police chief Jérôme Tallaron said.
The man is believed to have sought shelter inside his caravan after he was trapped by a fast-flowing current, the police chief told the AFP news agency.
“We found his car, which had been swept away by the flood,” Mr Tallaron continued, adding that so far rescue efforts had been “in vain”. Divers are also taking part in the search for the missing man.
His caravan was found “empty and in pieces,” a local police source added. The 136 children and teens from the German city of Leverkusen, for their part, were brought to safety.
Mr Tallaron added that one of the German children had suffered “severe” hypothermia but was expected to make a full recovery.
A 41-year-old man has been missing since Wednesday afternoon after powerful storms pummelled the French island of Corsica, about 105 miles (170km) from France’s southern coast.
Florian Bellin was last seen climbing up the Bocca di Chiralba, one of Corsica’s most treacherous mountains, local authorities said on Thursday.