At least 43 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 neighboring 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 been evacuated.
German Chancellor Angela Merkel, who is in the US ahead of a meeting with President Joe Biden, said she was “grieving those who have lost their lives” in the flooding.
“My thoughts are with you, and you can trust that all forces of our government – federal, regional and community – collectively will do everything under the most difficult conditions to save lives, alleviate dangers and to relieve distress.”
Malu Dreyer, chief of Germany’s Rhineland-Palatinate 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.”
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.
It said some houses had been completely cut-off and could no longer be reached by boat.
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.
Residents in the region told AFP news agency they were stunned by the disaster.
“Nobody was expecting this – where did all this rain come from? It’s crazy,” Annemarie Mueller, a 65-year-old resident of Mayen, said. “It made such a loud noise and given how fast it came down we thought it would break the door down.”
Local teacher Ortrud Meyer, 36, said she had “never seen anything like this”.