Schools have been closed, 5,500 people moved from their homes, rescue workers have been called out to help 10,000 people and some 80 roads have been partially closed as torrential rain, which killed four and caused havoc in Germany and Austria, hit much of France.
Eight departments were on orange alert Thursday and the Seine-et-Marne remained on red alert, although water levels on the river Loing started to subside at Nemours, where the centre of the town had been under water for more than a day and water and power was cut off for many homes.
Over 2,000 people have been placed in temporary accommodation, about 20 of them saved by a boat patrol overnight, according to mayor Valérie Lacroute.
At Melun, a major town south-east of Paris, the River Seine was still rising as heavy rain fell on Thursday morning.
In the Loiret department, which was taken off red alert on Thursday morning, the equivalent of six weeks' rain has fallen in three days, making road and rail access to the historic city of Orleans difficult and the A10 motorway closed in several places.
Emergency funds promised
Environment Minister Ségolène Royal, on a visit to Nemours, declared that a state of natural catastrophe, which gives immediate access to national emergency funding, would be declared and Ile de France regional president Valérie Pécresse announced an emergency fund of one million euros.
Prime Minister Manuel Valls, who had already visited the national crisis centre in Paris, and Interior Minister Bernard Cazeneuve visited Nemours later in the day and announced "exceptional" finance for local authorities who have to tackle the effects of the storms.
Valls warned of a "tense" situation in the Essonne department, west of Paris, with 2,000 evacuations expected at Longjumeau and Corbeil-Essonnes.
Seine rising at Paris
There was anxiety in Paris, too, as the River Seine continued to rise, submerging some railway lines, which were also affected by strike action.
The central Saint Michel station was closed due to flooding.
Paris city council said that "particular vigilance" was necessary with the danger of water levels reaching 5.10-5.70 metres - close to the 6.00 metres that brings a risk of serious flooding to the city.