The Government issued safety warnings today as the heaviest snowfall of the season crept in.
A light dusting across south east England this afternoon precedes up to 15cm (5.9ins) in areas around London overnight, forecasters warned.
Temperatures remained resolutely above freezing across the UK at lunchtime but they would plunge as low as minus 9C (15.8F) tonight in the Scottish Highlands, MeteoGroup UK, the weather arm of the Press Association, said.
With treacherous conditions during festive preparations, the Government warned the public to keep an eye on vulnerable members of communities.
Chances of a white Christmas continued to "hang in the balance", experts said.
Andy Ratcliffe, a forecaster for MeteoGroup UK, said snow was not settling in the UK today - but a heavier blanket was on its way.
"Parts of the UK have been hit by sleet rather than snow today," he said. "But tonight it's pretty certain to turn to heavier snow, particularly in the south-east.
"While there could be as little as 2cm in central London, areas just outside - particularly around the Chiltern Hills - could see as much as 15cm.
"Western Kent and Surrey will see snowy conditions into tomorrow.
"This could be the heaviest snowfall of the winter so far for areas."
Northamptonshire and northern parts of Hampshire were also identified as areas likely to wake up to a snowy scenes.
Public Health Minister Gillian Merron said: "Cold weather is especially dangerous for older people or those with serious illnesses.
"The Government's 'Keep Warm Keep Well' campaign gives important advice to older people on how to stay fit and healthy through the winter."
Leaflets were available in local GP's surgeries, pharmacies or council offices, she said.
Bookmakers have recently slashed the odds of a white Christmas.
Brendan Jones, a MeteoGroup UK senior forecaster, said: "There is the potential for milder air attempting to move northwards by midweek, but this in itself could bring further periods of snow.
"This battle ground between the very cold conditions, and milder air heading in from the south-west, could still be in place by Christmas day. The prospect of a white Christmas therefore hangs in the balance at the moment, although it should be noted that the chances of falling snow on the big day do appear to be greater than in recent years."
One gambler from Derbyshire stands to collect more than £14,000 if it snows on Christmas Day.
As temperatures continue to plunge, Yvonne Doyle, a regional director of public health, said: "Remembering the needs of friends, relatives and neighbours who could be at risk is essential.
"The elderly, and those who are ill, are particularly vulnerable during cold weather."
Andrew Harrop, of Age Concern and Help the Aged, also spoke of his concern for the elderly.
He said: "For older people, protection against the cold is vital. Last winter's cold snap sent excess winter mortality to a 10-year high, with around three quarters of excess winter deaths recorded among people aged 75 or over."
Kent Police warned motorists to prepare for poor driving conditions as ice was expected to hit some of the county's roads.
Chief Inspector Roscoe Walford said: "Motorists need to take the weather and road conditions into account when driving in wintry weather.
"If the weather is severe, please only travel if your journey is absolutely necessary."
Rail operator Southeastern said it was "working hard" to ensure a normal service would run during the forecast snow, but advised conditions might cause some disruption to services.Reuse content