Flood risk is expected to increase in several regions, while mountain conditions will deteriorate.
From Tuesday, rain and strong winds will spread nationwide, with the south-west particularly affected.
In the mountains, rain below 2,000m will increase snowmelt and runoff.
Conditions worsen midweek.
On Wednesday and Thursday, heavy showers and very strong westerly winds are forecast, with gusts reaching 100km/h along the Atlantic coast.
A deep low-pressure system on Thursday could cause local disruption.
Snow will fall at higher elevations, lowering later in the week.
By Friday, further rain and strong winds are expected, especially in western regions.
Rising river levels could lead to flooding in parts of Brittany and the west, while heavy snowfall will maintain a high avalanche risk in the mountains.
Cooler air arriving from the north will give a more wintry feel by the weekend.