Trees falling across railway lines also caused problems and there were warnings of flooding if rivers burst their banks.

The Met Office said gusts of wind could reach 70 mph to 80 mph in places in the afternoon and evening and advised people to take extra care.

"It is an Atlantic storm that is going to the north of the British Isles but causing windy conditions over much of the country," a Met Office forecaster said.

While the strongest winds hit north Wales and Scotland, trees were flattened across much of Britain, in part because heavy rain has loosened the soil and made trees more vulnerable.

Up to 80,000 homes in south and mid-Wales were without power after trees brought down power lines.

"The main areas affected are around Swansea, the Neath Valley, Pontypool and up into Powys," a spokeswoman for utility Western Power said.

She said emergency teams were trying to restore power, but the bad weather was hampering efforts.

"Normally we would use helicopters to check the power lines, but we can't do that at the moment because it is too windy."

FERRY CROSSINGS CANCELLED

Kent Police were forced to close parts of the M20 to stack freight lorries unable to get across to France because the severe weather closed Dover Port to inbound ferries.

High winds closed the M25's Dartford River Crossing bridge.

The storms also blew down trees at the Royal Botanic Gardens in Surrey forcing the World Heritage Site to be evacuated and shut to visitors.

"The damage to the collections at Kew is minor but our visitor's safety is our main priority," said spokeswoman Jill Preston.

Forecasters said the high winds would ease slightly overnight, but Friday will see renewed gusts spreading across the country from the west.

The Environment Agency has issued 55 flood warnings and the Highways Agency urged drivers to be cautious.

"All road users are advised to be aware of the sudden cross winds, but especially drivers of high sided vehicles and motorcyclists," it said on its Web site.

A number of roads have been closed because of overturned lorries and difficult driving condition were causing delays, some of them severe.