Five people have died as torrential rain and high winds brought serious flooding to south-eastern France.
Local roads are described as "death traps"
Forecasters warned of further downpours, as the floods blocked roads, disrupted rail services and forced more than 9,000 people to flee their homes.
France's second-biggest city Marseille was declared a disaster area.
After visiting the worst-affected area, French President Jacques Chirac said the victims could count on the solidarity of the rest of the nation.
The French Government announced it was giving 12 million euros ($14m) in initial emergency fund for the region.
As well as disruption to schools, roads and transport, several nuclear reactors were shut down because of vegetation clogging the rivers used to cool them.
Rescue services in Marseille used barges to evacuate 1,000 people from a northern suburb. Firefighters in the city answered 500 emergency calls.
"In the face of this new catastrophe, my thoughts go to the victims and those who have lost everything," President Chirac said in the town of Valabre.
Earlier, Environment Minister Roselyne Bachelot said all public emergency services had been mobilised.
She urged motorists not to use the roads during the heavy rains.
"Roads are death traps whenever there are floods," she said.
On Wednesday, authorities confirmed that five people had died.
The announcement followed the discovery of the bodies of a 53-year-old woman who had been swept away on Monday night near Lyon, and of an elderly man in Marseille.
On Tuesday, police and rescuers recovered the bodies of three other
victims in the Marseille region.
One man was found trapped in a flooded underground tunnel in the port city and another had fallen into a raging river in nearby Orange.
The national weather service, Meteo France, has issued a high-level alert for 12 administrative departments in the region.
The service expects the incessant rains and winds of up to 150 kilometres per hour (90 miles per hour) to continue until Thursday.
Officials are anxiously watching the situation in the Rhone Valley amid fears of further flooding.
The country is also battling a flu outbreak. Officials said two million cases were expected by the end of the week.
Some emergency departments in the Paris area have been filled to overflowing with flu victims, many of them children.
Read a selection of your comments below.
I'm living and studying in Montpellier for a year, and just recently the weather here is making me feel right at home - literally torrential stuff, about 3 months' worth of rain in as many days. Although it's stopped now. Uni was closed yesterday and today, and there was a good 2-3 cms of flooding in some classrooms - though obviously I only found out AFTER arriving on time for class... The walk there was quite an adventure - roads have turned into gullies practically, and the trams/buses are running only just or not at all.
Alain, Montpellier, France
Although a couple of hundred kilometres from Marseille it is likewise 'bucketing it down' in our village near Narbonne. Having suffered from two and a half metres of water in our house in October 2002 due to flash flooding we are now intently watching the storm channel which flows through our village. We know what it is like to have been flooded here and our thoughts go out to the people who are now suffering.
Michelle Marsh, France
Living and working in Montpellier, the journey to work this morning was fraught, with flooded roads and incautious drivers. At 11h00 we were sent home as Meteo France raised a red alert (the first?). A number of broken down cars line the roads. The outskirting towns are cut off from us.
It rained all day yesterday and last night - the rain here is not generally the polite English variety but a much more forward Gallic version, with sound effects (son et lumiere indeed!). It is no longer raining - but it looks like the wind will start up.
David K-M, France
Big fires and big heat in the Summer, big floods in the autumn... what next?!
What a rotten year!