Heavy snow that lasted for more than three hours on Saturday forced London's two main airports to close their runways and snarled road and air traffic in many other parts of England.

Shoppers walk along Oxford Street, in central London December 18, 2010. Fresh snow brought much of Britain to a standstill on Saturday, on what is traditionally the busiest weekend for shopping and travel in the run-up to Christmas. [Xinhua/Reuters]

London's Gatwick airport closed its runway despite the efforts of 150 staff using 47 snow plows, while British Airways suspended all flights from Heathrow.

Gatwick officials said the runway closure would continue until at least 3 p.m., while Heathrow did not say when operations there would resume.

Heathrow Airport said it closed the runways to clear snow and to keep the airport safe, advising passengers to check with airlines before travelling to the airport.

"Heathrow is fully operational but we are expecting more snow and planning for the worst," the airport, Europe's busiest, said in a statement. "BA passengers must stay at home as all BA flights are canceled. At this time there are no significant delays at other terminals."

Other airports in Britain were also disrupted by snow and ice, including London City, Birmingham, Bristol, and Exeter.

The Met Office of Britain issued a flash warning for heavy snow for the London area and parts of Southeastern England, warning "it could give 20 to 25cm of snow in some parts."

Mark Seltzer, a weather forecaster with Britain's Met Office, said the U.K. may experience its coldest December on record.

"Temperatures will struggle to get over freezing and although the snow should ease off tonight, it will return to eastern areas on Sunday," he said.

Hundreds of motorists were left stranded on the major M6 route in northwestern England following a deluge, prompting police patrols to offer food and water to drivers.

Darron Burness, of Britain's Automobile Association, said conditions on U.K. roads were treacherous. "One of the biggest problems is that large amounts of snow are falling very quickly on to frozen surfaces, making driving hazardous," he told The Associated Press.

The Saturday before Christmas is traditionally one of the busiest travel days of the year, but motorists have been warned that virtually no part of the country will be unaffected.

Horse racing meetings and dozens of soccer games in England and Scotland were called off as a result of the conditions, including a high profile match scheduled for Sunday in London between Chelsea and Manchester United.

Heavy snow hit northern parts of Britain on Friday, northwestern England and Northern Ireland the worst hit, stranding hundreds of drivers on the roads and forcing one-quarter of trains delayed or canceled.