At least 120 people have died and hundreds more in western Europe are unaccounted for after some of the worst flooding in decades.
Record rainfall caused rivers to burst their banks, devastating the region.
In Germany, where the death toll now stands at over 100, Chancellor Angela Merkel called for a determined battle against climate change.
Belgian media is reporting 22 deaths there. The Netherlands, Luxembourg and Switzerland are also affected.
In Germany, the states of Rhineland-Palatinate and North Rhine-Westphalia were the worst-hit.
Scientists have repeatedly warned that human-induced climate change would bring pulses of extreme rainfall such as this one.
German President Frank Walter Steinmeier also called for action on climate change, saying: "Only if we take up the fight against climate change decisively will we be able to keep extreme weather conditions such as we are experiencing now in check."
In the western German district of Ahrweiler, up to 1,300 people are unaccounted for, the authorities say. A spokeswoman for the local government said mobile networks had been put out of action, making it impossible to contact many people.
The village of Schuld (population 700) was almost entirely destroyed. In the town of Erfstadt-Blessem, near Cologne, floodwaters caused a row of houses to collapse. Local authorities said they were receiving emergency calls from people trapped by floodwater but rescue was in many cases not possible.
In the town of Sinzig, 12 out of 35 residents in a care home for disabled people died after flood waters swept through the building as they slept.
A major dam near the Belgian border, the Rurtalsperre, overflowed slightly but did not break, officials said.
Some 15,000 police, soldiers and emergency service workers have been deployed in Germany to help with the search and rescue, while helicopters picked stranded residents from roof tops and tanks cleared roads of fallen trees and debris.
Speaking during a meeting with US President Joe Biden in Washington DC, Mrs Merkel expressed her "deepest condolences" and pledge government support for the rescue efforts.
The interior minister of North Rhine-Westphalia said it was impossible to give a clear number of casualties, adding that many people had "lost everything".
In Belgium, dramatic footage of the floods showed cars being swept away along a street in the city of Verviers. A curfew was in place overnight because of the risk of looting.
Residents of Liège, Belgium's third-largest urban area after Brussels and Antwerp, were ordered to evacuate. Local officials said those unable to leave should move to the upper floors of their buildings.
The Meuse river, which flows through the city, stabilised on Friday morning, with small overflows in some areas.
In the Netherlands, the town of Valkenburg was one of the worst affected, where flooding forced the evacuation of several nursing homes.
Households have built makeshift dikes out of shopping bags filled with sand and a bridge has collapsed. Fire crews are pumping water from beneath the toppled slabs of concrete to access a gas pipe and stem a leak.
The country has reported no casualties but thousands of people in towns and villages along the Meuse river have been urged to leave their houses quickly.
In the Dutch city of Maastricht, 10,000 people were ordered to evacuate late on Thursday.
On Friday, residents of the southern town of Meerssen was sent an online alert telling them to "immediately leave your home and get to safety".
The warning added that flood water had broken through a dike, and was about to swamp the surrounding villages of Bünde, Voulwames, Brommelen and Geulle.
The river running through the Swiss capital Bern burst its banks, flowing at a record rate of 560 cubic metres a second on Friday.
Lake Lucerne is flooding into the town and in Basel residents have been told to keep well away from the River Rhine. There is also the risk of mud and rock slides in the Alps as the flood waters run off.