Germany's Frankfurt Airport was hastily arranging alternative flights for passengers on Thursday, as torrential rain caused widespread disruption.
Authorities reported flooding on runways, which led to dozens of flights being cancelled.
By the usual 11pm cut-off time for flights, about 70 had been cancelled, with an additional 23 redirected.
“For more than two hours, ground handling was brought to a standstill,” an airport spokesman said.
Footage from Frankfurt Airport on social media showed planes surrounded by water.
Some passengers found themselves sleeping on makeshift camp beds, while many took refuge at the airport hotel.
“Today, the situation will probably stabilise again … There are still passengers here who need to be booked on to new flights,” the spokesman said.
Southwestern and central Germany also faced challenges.
Streets became rivers and basements resembled pools.
In the western Ruhr district's Gelsenkirchen, the situation became dire. The fire service reported rescues from submerged cars as many motorway underpasses became overwhelmed by water.
The fire service in Germany's financial capital reported more than 500 operations related to the storm, from flooded buildings to fallen trees.
Gelsenkirchen was particularly hard-hit, with streets and residences being inundated, and trees crashing on to vehicles. Emergency workers undertook boat rescues in some of the most affected areas.
The disruption in Germany is part of broader extreme weather in Europe.
As heatwaves spread across the continent, wildfires rage on Spain's Tenerife, leading to mass evacuations.
In France, cities like Lyon and Grenoble have been issued dire warnings, with the European meteorological network cautioning that “everyone is in danger, even those in good health”.
