Some people have already been out sledging

As predicted, snowfall has hit parts of northern Scotland and is expected to sweep south across much of the country over the next two days.

The Met Office said at least 15cm of snow could fall in northern Scotland, parts of Northern Ireland, south west Wales and parts of south west England.

The Highways Agency said drivers should prepare themselves and their cars.

The Met Office said Scotland's heavy wintry showers will move south into Northern Ireland on Thursday afternoon, then into west Wales and south west England on Thursday night and Friday morning.

The office's warning said: "Showers will fall widely as snow with local blizzard conditions, especially over high ground.

"Exposed coastal zones are expected to keep a mix of rain, sleet or hail leading to icy conditions."

Motorway gritters

The Highways Agency says gritters will be used on England's motorways and other strategic roads where ice or snow is expected.

It is advising drivers to check for up-to-date information before setting off on their journeys.

In Scotland, four walkers stranded on Wednesday night in freezing conditions on the Cairngorms have been found safe.

The men, in their thirties and believed to be from the Dundee area, contacted police using a mobile phone.

They were believed to have been sheltering in survival bags, on top of the 4,300ft Ben Macdui mountain.

Meanwhile, power firm Scottish Hydro Electric has warned of possible widespread damage to the electricity network.

It has drafted extra engineers into strategic points throughout Scotland, including the Western Isles.

Helicopters are also on standby to ferry the engineers to where they are needed.

Also in Scotland, a Highland Council spokesman said there had been no school closures, but head teachers were continue to monitor the situation.

The council has 230 of its staff ready to operate snowploughs and gritters.

Sledging

Meanwhile, some people are already taking advantage of the first snowfall by sledging.

One firm reported being "inundated" with orders for toboggans.

Patrick Polglase, managing director of Bouncy Happy People in Mylor, Cornwall, said there had been orders from across the country, including Surrey, Essex, Lincolnshire and Northamptonshire.

"We've sold more in the last two days than we have done in the whole of this year, so we're really looking forward to seeing if it does snow," he said.

During severe weather in January 2003, the Highways Agency was criticised for its handling of icy conditions on stretches of motorway in Hertfordshire and Essex.

At the end of that month, hundreds of people were left trapped in snow overnight on the M11 in Essex.

The agency says it has since revised its procedures and has its contractors on alert.

"We have survived two winters without major incident on the motorways and A roads," said a spokeswoman for the agency.

Do you have any pictures of the UK wintry weather? If so, you can send them to yourpics@bbc.co.uk or MMS them to 07725 100 100