Rivers in Europe have burst their banks from Paris to the southern German state of Bavaria, killing six people and trapping thousands more in homes and cars.
In France, authorities say areas along the Loing River, a tributary of the Seine River, are facing water levels unseen since 1910, when a massive flood swamped the French capital.
About 25,000 homes are without electricity because of floods in the Paris region and central France and more rain is forecast for the coming days, and authorities in Paris predict the Seine River will not reach its peak until Friday.
France's meteorological service said severe flood watches are in effect in two Paris-area regions: Loiret and Seine-et-Marne. Eight more regions, including three on the German border, face flood warnings as well.
Tourist boat cruises have been cancelled and several roads in and around the capital are under water. Days of heavy rain have caused exceptional delays to the French Open tennis tournament and may force it into a third week.
Authorities shut down a suburban train line that runs alongside the Seine in central Paris, serving popular tourist sites like the Eiffel Tower, the Invalides plaza and the Orsay museum. Other subway lines in Paris are running normally despite the flooding.
In the Loire valley in central France, the renowned castles of Chambord and Azay-le-Rideau were closed to the public because of floods in their parks.
Fara Pelarek, 44-year-old Australian tourist visiting Paris, said she was "very surprised" to see the Seine so high.
"I remember walking down below (before) and it was very easy," she said. "In a way, it's kind of nature taking over."
The rain that has fallen across Western Europe this week has already killed six people, including an 86-year-old woman who died in her flooded home in Souppes-sur-Loing southeast of Paris, the French government said.
German Chancellor Angela Merkel, meanwhile, is promising continued help for flooded areas of southern Germany, where five people were killed amid floods that swept through the southern towns of Simbach am Inn and Triftern near the Austrian border on Wednesday.
Mrs Merkel told reporters in Berlin on that she "mourns for those for whom the help has come too late, who lost their lives in the flooding".
She said disaster relief is on hand to help control the floods and rebuild damaged areas. The floodwaters in Bavaria receded on Thursday and disaster relief crews were helping to clear the wreckage, but there are warnings of more storms.
For the second day, emergency workers evacuated residents in Nemours, 50 miles south of Paris, the hardest-hit site in France.
In the southern Paris suburb of Longjumeau, fire fighters drove in a Land Rover through flooded streets, telling trapped residents to wait for help. On the town's main street, shopkeepers tried to sweep the water out of their shops.
Belgium also endured a fourth day of heavy rain, with flooding reported in several areas. After widespread flooding hit northern Antwerp and the west of Flanders early in the week, waters kept rising in eastern areas around Limburg and Liege. Several neighbourhoods have had to be evacuated as cellars flooded and streets were submerged.
A major train line linking eastern Limburg to the capital of Brussels had to be temporarily suspended early on Thursday