Berlin - Hail damaged roofs and cars, and torrential rain caused flash floods in parts of Western Europe early Friday as hot air masses triggered the first summer thunderstorms of the season.

Along Germany's western rim, streams burst their banks, flooding low-lying houses and washing mud onto roads during the night.

In the German city of Krefeld, near the Dutch border, hailstones as big as tennis balls dented dozens of parked cars and smashed skylights in houses.

Further east in the state of Hesse, violent gusts toppled trees onto a national two-lane highway near Bad Schwalbach.

Fire-fighters evacuated motorists stranded on the road, saying it would take until Tuesday to clear the debris and reopen the highway.

A clear-up operation was under way in parts of south-west Britain following flash floods that led to homes being evacuated and people being rescued from cars stranded in the floods the previous evening.

A sudden heavy burst of torrential rain hit the counties of Devon and Somerset, lasting for about 30 minutes, the emergency services said.

Some homes were damaged but the number of people being evacuated was small and most had found refuge with relatives.

"It was a typical flash flood gone almost as soon as quickly as it came. A tremendous amount of water came down with very little warning and the surface water drainage couldn't handle it," fire service spokesman Andy Newland said. (dpa)