Floodwaters have reached a peak in Paris and are now threatening towns downstream along the rain-engorged Seine River.

The national flood monitoring agency Vigicrues said the water levels hit a maximum height of 5.84 metres (19ft 2in) on the Austerlitz Scale early on Monday.

That is beneath the level feared by forecasters last week, and well below record levels of 8.62 metres (28ft 3in) in 1910.

A flooded street lamp next to the river Seine in Paris (AP)
A flooded street lamp next to the river Seine in Paris (AP)

Weeks of heavy rains have swollen the Seine and its tributaries, forcing road closures, engulfing scenic embankments and halting river boat cruises through the French capital.

The waters are expected to stay unusually high for days or even weeks.

The floods have caused damage in 242 towns along the river, and are now threatening more towns as the Seine heads downstream west of Paris toward Normandy and the English Channel.