A storm swell in the Mediterranean off the port city of Sete in southern France overturned three boats, killing one amateur sailor and putting another in the hospital in critical condition, said Herault department authorities.
Some 64,000 people in the south of France were also left without power, network supplier Enedis told AFP, while several departments reported roads cut off by floodwaters.
Following a crisis response meeting in Paris, Energy and Ecological Transition Minister Agnes Pannier-Runacher told journalists the government was mobilizing "all state services" and urged citizens to be careful.
"These episodes will have a tendency to recur. We're living at a time when climate change is making itself felt in concrete ways in our daily lives," she said.
Authorities put the Seine-et-Marne department near Paris on red alert for flooding as the rain swelled the Grand Morin river, a tributary of the Seine, which runs through the French capital.
Another 29 of the country's departments were placed on orange alert, with heavy rains and high winds expected.
There were 35,000 households that lost electricity in the worst-hit department of Pyrenees-Atlantiques, with a clutch of other departments in the southwest and central east of the country also affected, Enedis said.
Weather forecasters had predicted the storm would dump a month's worth of rain on a swathe of the country, including Paris.
Portugal's civil protection authority reported more than 1,300 incidents overnight Tuesday to Wednesday, three-quarters of which involved fallen trees in the north of the country.
Porto, the main northern city, was hit hardest, with 400 trees uprooted. Cars were also damaged and rail services interrupted near Barcelos, also in the north.
The storm also cut power to more than 300,000 households, said the country's electricity supplier.
Weather and civil protection officials, having predicted winds of up to 120 kilometers per hour (75 mph) and heavy rain, put the coast on a yellow alert, as waves reached up to seven meters (23 feet) high.
Spanish weather officials issued an orange alert for the north and northwest of the country, warning of winds of up to 140 kilometers per hour in the Asturias region.
Galicia, in the northwest, reported some roads blocked by mud slides and fallen trees in urban areas.
SD/