Eighteen people were confirmed dead in France over the weekend, according to Major Samuel Bernes, a spokesperson for the civil defence force.
In Spain authorities said on Sunday that two men were killed when their car was hit by a falling tree. Another woman lost her life when a wall collapsed in the Galicia region, while a boy in Portugal died after being hit by a falling branch.
The storms crashed into France and Spain’s western coasts overnight, with bad weather conditions stretching from Portugal to the Netherlands.
Some residents sought refuge on their rooftops as flood water spread inland, others sheltered upstairs as Xynthia smashed windows and brought down power lines.
A blackout fell across a 500 kilometre area from the Brittany peninsula to the highlands of the Massif Central.
At Paris Charles de Gaulle airport around 100 flights were cancelled and some French roads were closed to heavy goods vehicles.
The storm developed in the Atlantic Ocean near the Portuguese island of Madeira, which is still recovering from the effects of flash floods that killed 42 people last week.