Torrential rain forced thousands of people from their homes just south of Paris while the River Seine surged to its highest level in more than 30 years in the French capital, shutting down the famed Louvre and Orsay museums and a metro line after a cloudburst caused the Loire and Seine rivers to overflow their banks.
"Since yesterday it's just been a deluge," said Jerome Coiffier, an inhabitant of Longjumeau, less than 20 km (13 miles) south of Paris, where firemen wading thigh-deep in water rescued inhabitants using inflatable boats.
At least 3,000 out of 13,000 inhabitants were evacuated in Nemours, 75 km (45 miles) south of Paris, as floodwaters crept toward the second story of buildings in the town center.
Prolonged heavy rain also pounded parts of neighboring Germany and at least five people have died in floods in Bavaria state in the south of the country, officials said.
In Paris, the Seine rose above 5 meters (16 feet), forcing the SNCF rail operator to close a commuter line that runs along the river and is used by tourists to reach the Eiffel Tower and Notre-Dame Cathedral.
Meanwhile, the Louvre museum shut down and said it would remain closed on Friday to keep its priceless art safe. The Orsay museum of Impressionist art will also be shut on Friday. Both are located right by the Seine in central Paris.
The Seine could peak at 6 meters (nearly 20 feet) in Paris on Friday, officials said, stressing that was still well below the level where it would pose danger to residents. The river reached a record high of 8.6 meters (28 feet) in 1910.
President Francois Hollande declared a state of emergency in the worst affected areas and promised funding to help local authorities deal with flood damage. Unusually heavy rains in June showed the urgency to curb climate change, he said.
In the Loire Valley, Chambord castle, a UNESCO world heritage site, found itself surrounded by water.
The national weather service said the greater Paris region had in May endured its wettest month since 1960.
In the Loiret region, where local officials called on the Army to help evacuate motorists trapped on the A10 motorway, the floods were the most severe in a century.
Meanwhile, in Germany at least five people have been killed in floods caused by prolonged heavy rain in the southern Bavaria state and thousands of households were cut off from electricity, officials said on Thursday.
At least four people were missing in the district of Rottal-Inn. "We're expecting the worst," police spokesman Michael Emmer said, adding divers were searching for those missing.
Flooding has affected an area of around 160 square kilometers near the border with Austria and had caused damage worth tens of millions of euros, officials said.
District governor Michael Fahmueller described the destruction as "scenes of horror."
"We have had floods before, but this time it is so much worse. We had been rebuilding everything for a year, so (our) house was newly renovated from top to bottom, and it is all ruined again," Sieglinde Simboeck told Reuters TV.
Police arrested two looters who tried to snatch car radios. Several thousand households were cut off from electricity in the flooded region close to the Austrian border. An emergency allowance of 1,500 euros ($1,678) will be provided immediately to the hardest-hit victims, a government official announced.
Weather forecasters said more rain was expected in the region on Thursday, further complicating rescue efforts.
Parts of the northern, heavily industrial state of North Rhine-Westphalia have also experienced serious flooding.
Earlier this week, three people were killed in floods in the southwestern state of Baden-Wuerttemberg and a young girl was killed by a train as she took shelter from the rain under a railway bridge.
Additional reporting by Sybille de La Hamaide and Emmanuel Jarry in Paris.