With heavy rain expected, nine French departments were on orange alert for floodiung, the Météo France weather forecaster announced early Friday morning.
They were Pyrénées-Atlantiques, the Landes, Gironde, Charente-Maritime, Loire-Atlantique and the Vendée in the central and south-west and Morbihan, Finistère and Côtes-d'Armor in Brittany.
"In a context of exceptionally high tides and a damaged coast, a combination of particularly high sea levels and strong waves make particularly neccessary," Météo France explained.
The Morlaix and Laïta rivers in Finistère were likely to burst their banks at high tide, it pointed out.
Storms hit west France in December and earlier this month, causing considerable damage and flooding and further weakening coastal defences.
Météo France also predicted heavy snow in Alpes-de-Haute-Provence, Hautes-Alpes and Alpes-Maritimes.