The Herminia depression earlier this week unleashed downpours on northwestern France, sparking some of the worst floods in decades.

Surrounded by two rivers, a canal and marshes, several parts of the town of Redon in Brittany have been sitting in water since Wednesday.

The Vilaine river's level was on Thursday morning hovering just below that of historic floods in 2001, but was expected to rise further during the day, official alert body Vigicrues reported.

Its projections could see the river surge to near a level not seen since 1936.

"It's highly likely that the peak won't be reached today, but it will be in the next few days," said Redon's Mayor Pascal Duchene.

He said an estimated 750 residents could be affected.

The Red Cross had set up an emergency shelter for 50 people at a local gym, with camp beds lined in a row and tables and chairs set up under its basketball hoops.

A second shelter was being set up at another sports centre for 200 people, a Red Cross official said.

Adeline Bernard, 29, was one of the first people to find refuge at the sport hall.

"When I saw that the electricity was going to cut, and that the water was rising, I thought: 'That's it, I'm out of here,'" she said.

Isabelle Rousselet, 66, said she was happy to be living in a higher part of town.

"It will take time for it to all drain away. It's a bit scary," she said.

In a flooded part of town, one resident waded through the water at the bottom of her home in rubber boots, while another wobbled along long planks of wood balanced over cinder blocks at one street corner.

In the adjacent town of Saint-Nicolas-de-Redon, on the other side of a flooded bridge, police had evacuated 300 people.

In total, around 1,600 people have been forced to leave their homes in the wider region.

President Emmanuel Macron assured on X on Thursday his "solidarity with resident of the west" of France.

Minister of Ecological Transition Agnes Pannier-Runacher said she expected a "state of natural disaster" in coming days.

Scientists have shown that climate change caused by humans burning fossil fuels is making storms more severe, super-charged by warmer oceans.

Herminia, which brought on the heavy weather over western France, follows Storm Eowyn that hit Ireland and Britain before the weekend.

Its impact on France's northwestern regions was exacerbated by the fact that the ground was already drenched from previous persistent rainfall.