Large areas of Tuscany have been hit by flooding, leaving five people dead and several others missing, as heavy winds and rain buffeted central Italy.
Cars were swept away as the River Bisenzio flooded and people climbed on to roofs to escape the deluge.
Four hospitals were flooded, people were trapped in their cars in underpasses and the west coast was lashed by high waves.
Storm Ciarán has caused more than 12 deaths across Western Europe.
Winds of 207km/h (129 mph) were recorded earlier on the north-west coast of France, as the storm also lashed southern England, Belgium, the Netherlands and Germany, as well as the Atlantic coast of Spain and Portugal.
A five-year-old child was one of two people killed in Belgium by falling trees.
Power lines went down and transport was severely disrupted. Residents had to be evacuated from their homes on the Channel Island of Jersey.
The storm reached Tuscany on Thursday night, and regional governor Eugenio Giani declared a state of emergency as winds reached 140km/h.
Livorno on the coast and the towns of Prato and Montemurlo near Florence were among the worst affected areas.
In Montemurlo, officials said on Friday that 200mm (7.8in) of rain had fallen since Thursday afternoon and the Bisenzio river burst its banks in two places.
An 85-year-old man was found dead on the ground floor of his flooded home. Rescuers believe he had been unable to climb the stairs to safety.
The governor of Tuscany shared a video showing cars being swept away by floodwater and appealed for people to go to upper floors. He described the rainfall as "unprecedented in the past 100 years".
Close to the river, in Campi Bisenzio, people climbed on to their roofs to get to safety and about 100 staff and customers sought refuge in a shopping centre.
Among those missing were a couple whose car was found overturned in Vinci, to the west of Florence. There had been fears that the River Arno would flood in Florence but the emergency appeared to have subsided by mid-morning.
The mayor of Prato, Matteo Biffoni, described overnight events as a "blow to the stomach". Floods left entire areas submerged and the ground floor of the town's Santo Stefano hospital was partially flooded.
The west coast was lashed by waves reaching 3.5m, and Milan was hit by flooding for a second time this week, three days after the River Seveso burst its banks.
The storm also caused damage in the north-eastern region of Veneto, where one person was missing and Governor Luca Zaia said 160mm of rain had fallen in 24 hours.
Further east, there were red weather alerts in Slovenia and Croatia. Forecasters warned of high winds, hail and thunderstorms and authorities in Slovenia warned of one of the strongest cyclones in the past 10 years.
