The Seine is expected to reach a peak of up to 6.2 metres (20.3 feet) in the capital this Saturday on a scale used to measure its levels, four to five metres above its normal height.
The December-January period is now the third-wettest on record since data collection began in 1900, according to Meteo France.
Many regions have seen double the rainfall than normal, including Paris where 183 millimetres (7.2 inches) have been dumped since December 1. More rain was forecast for Thursday.
While the Seine is set to reach levels last seen in 1982 at its peak on Saturday, it flows in a deep channel through the heart of the capital, posing a danger only to riverside buildings and infrastructure.
Areas on the outskirts are under water, however, including the southern suburb of Villeneuve-Saint-Georges where people are using boats to get around flooded streets. Parked cars were nearly completely submerged.
"After the floods of 2016 it took us nearly two years to repair the damage. We just finished, and now we're going to have to start all over again," said Akca, 31.
Just down the street, 21-year-old Carlos said his basement was already completely full. "It's a swimming pool," he said.
About 150 residents forced from their homes are being housed in a gymnasium, the prefecture said.
For the greater Paris region as a whole, some 400 people have been evacuated and nearly 1,000 people were without electricity.
No relief soon
All boat traffic on the Seine in Paris and upstream has been stopped, keeping tourists off the capital's famed sightseeing boats.
Debbie Komorowski from Adelaide, Australia, was visiting the city for the fifth time with her husband and was left disappointed.
"Two years ago we had our wedding anniversary here, on the bench over there," she told AFP on the Ile de la Cite island in the heart of the capital. "And now it's gone! We can't believe it. It's amazing and sad to see."
Metro stations might be closed as the Seine keeps rising, and services have been halted on the busy RER C suburban line until next Wednesday as workers seal off ventilation ducts to keep water out.
"It's likely that the Seine will stay high for several days next week," said Marc Mortureux, risk prevention director at the French environment ministry.
Three riverside museums -- the Louvre, the Musee d'Orsay and the Orangerie -- have said they are preparing for flooding, though only the Louvre has had to close off a wing, to move works from its Islamic art department to higher ground.
But the Louvre is better prepared since the flooding of June 2016, when it enlisted 170 volunteers to transfer 35,000 works -- about a quarter of the total kept in basement areas vulnerable to flooding -- in just 48 hours.
The task closed the doors to the world's most visited museum for four days.
Since then it has started building a conservation site near the northern city of Lens for vulnerable works, but the 60 million euro ($75 million) facility is not expected to open until summer 2019.
Most other Paris museums were unaffected, though a National Library wing near Notre Dame was closed Thursday to move works to higher floors, and was to reopen Friday.
More alarming for Parisians are the rats being flushed out of the sewers, making the city's rodent population much more visible.
"That doesn't mean there are more of them, only that we see them more often," said Pierre Falgayrac, an expert in urban rodents, who says the capital is now home to 1.75 rats for every Parisian.
Rivers were also spilling their banks across 13 northern and eastern French departments still on flood alert, though the Rhine, which was completely closed to traffic Tuesday, has been reopened south of Strasbourg.
The Rhine, which originates in Switzerland and flows into the North Sea via Germany and the Netherlands, began receding from the peak reached Tuesday after officials emptied some seven million cubic metres (247 million cubic feet) into a flood containment zone.
In the central Yonne department about 40 roads were closed due to flooding which the prefecture warned was likely to worsen in coming days.
Higher rivers are relatively common in winter, "but the extent makes this an exceptional event", Mortureux said.