The worst of the flooding has been in the state of Rhineland-Palatinate, where around 50 people have been waiting on rooftops to be rescued.
At least six people have died and 30 people are missing in the hilly Eifel region after several homes collapsed, following severe floods in western Germany, police say.
Much of the flooding was triggered when the Ahr river, which flows into the Rhine, burst its banks south of Bonn.
Malu Dreyer, chief of the 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.”
Police helicopters and the army have been deployed to some areas to help stranded residents.
Some schools have been closed, while rail and road transport links have been severely disrupted around the west of the country.
About 25 houses are in danger of collapsing in the district of Schuld bei Adenau in the Eifel region, where a state of emergency has been declared, according to SWR.
It said some houses had been completely cut-off and could no longer be reached by boat.
Four people died in the Eifel region when their homes were swept away in the early hours of Thursday, police said.
Meanwhile, two firefighters died on Wednesday in the neighbouring state of North Rhine-Westphalia. One drowned, while the other reportedly collapsed following a rescue operation.
Neighbouring Belgium has also been hit by flash floods, and dramatic video showed cars being swept away along a street in the city of Verviers.
Almost 2,000 people have been forced to evacuate in the town of Chaudfontaine, the Le Soir newspaper reported.
Rail services in the southern half of Belgium have been suspended because of the extreme weather.
In the Netherlands, the province of Limburg has been left heavily flooded following downpours overnight. Power
Forecasts suggest more heavy rain is due in much of Germany and Belgium on Thursday and Friday.
Experts say that climate change is expected to increase the frequency of extreme weather events, but linking any single event to global warming is complicated.
Source : BBC