At least 42 people have died in western Germany and many more are missing following severe floods, police say.
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 six others have died in neighbouring Belgium, and the city of Liège has urged all residents to leave.
It follows record rainfall in parts of western Europe that has caused major rivers to burst their banks.
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 also had to be evacuated.
Malu Dreyer, chief of Germany’s Rhineland-Palatinate state, described the flooding as a “catastrophe”.
Chancellor Angela Merkel, who is in the US ahead of a meeting with President Joe Biden, said she was “shocked by the disaster”.
At least 19 people died in the Ahrweiler district of Rhineland-Palatinate, after the Ahr river, which flows into the Rhine, burst its banks.
Police helicopters and hundreds of soldiers have been deployed to some areas to help stranded residents. Earlier, police said dozens of people were waiting on rooftops to be rescued.
Schools have been closed around the west of the country, while transport links have been severely disrupted.
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.
Eight deaths were reported in the district of Euskirchen in North Rhine-Westphalia, while four people died in the Eifel region when their homes were swept away.
Meanwhile, two firefighters died on Wednesday in North Rhine-Westphalia. One drowned, while the other reportedly collapsed following a rescue operation.
Belgium has also been hit by flash floods, and dramatic video showed cars being swept away along a street in the city of Verviers.