At least 33 people have died in western Germany and many more are missing following severe floods, police say.
Record rainfall in many parts of western Europe has caused major rivers to burst their banks.
The worst of the flooding has been in the states of Rhineland-Palatinate and North Rhine-Westphalia, where buildings and cars have been washed away.
At least 19 people died in the Ahrweiler district of Rhineland-Palatinate, after the Ahr river, which flows into the Rhine, burst its banks.
Two firefighters died on Wednesday in the state. One drowned, while the other reportedly collapsed following a rescue operation.
Malu Dreyer, chief of the state, described the flooding as a “catastrophe”.
“There are dead, missing and many people still in danger,” she said. “All of our emergency services are in action round the clock and risking their own lives.”
German Chancellor Angela Merkel, who is in the US ahead of a meeting with President Joe Biden, said she was “shocked” by the disaster.
Police helicopters and hundreds of soldiers have been deployed to many areas to help stranded residents. Earlier, police said dozens of people were waiting on rooftops to be rescued.
About 25 houses are in danger of collapsing in the district of Schuld bei Adenau in the mountainous Eifel region, where a state of emergency has been declared, according to German broadcaster SWR, which said some houses had been completely cut-off and could no longer be reached by boat.
Belgium has also been hit by flash floods, and dramatic video showed cars being swept away along a street in the city of Verviers. In the town of Pepinster, 10 houses collapsed after the River Vesdre burst its banks.
The city of Liège has urged all residents to leave. Almost 2,000 people were forced to evacuate in the town of Chaudfontaine, Belgium’s Le Soir newspaper reported. Rail services in the southern half of Belgium have been suspended because of the extreme weather.
The Netherlands has also been badly hit, with flooding rivers damaging many houses in the southern province of Limburg. A number of care homes have had to be evacuated.
Forecasts suggest more heavy rain is due in much of western Europe on Thursday and Friday.