The swollen River Seine in the French capital, Paris, has peaked at more than four metres above its normal level.
It rose to 5.84m (19.2ft) early on Monday, and is not expected to begin receding before Tuesday.
Weeks of rainfall have produced a relentless rise in the water level.
Around 1,500 people have been evacuated from their homes in the greater Paris region, while a similar number of homes remain without electricity, the authorities say.
In 2016, the last significant flood in Paris, the river reached a high of 6.1m.
Seven stations of a main commuter line, the RER C, have now been closed until at least 5 February, and some expressways that run alongside the Seine have been closed.
The city's famous Bateaux Mouches tourist boats are out of service, with only emergency services allowed to use the river.
At the Louvre, a lower level housing Islamic artwork was closed to visitors. Other famous attractions like the Musée d'Orsay and the Orangerie gallery were on high alert.
Several areas on the city's outskirts are under water, and some residents are getting around by boat while dozens have been evacuated from their homes. Some schools are closed.
"Everyone is getting around by boat" on the island of Migneaux in Poissy, a western Paris suburb, said local Serge Matikhine.
"The mood is still good, we are used to it - in 20 years we are on our eighth or ninth flood," he told the AFP news agency.
Water levels are expected to remain high all week, as more rain is expected to worsen an already waterlogged soil.