Prospects of a white Christmas are "greater than they have been for a number of years" with temperatures continuing to plunge towards the festive period, forecasters have said.
Bitterly cold conditions will deliver widespread snowfall in the coming days as the mercury consistently sinks to -5C (23F).
Brendan Jones, senior forecaster from MeteoGroup UK, the weather arm of the Press Association, said the UK will shiver in its "first major taste of winter through the coming week", with "bitterly cold conditions, hard frosts and snow in many areas".
East to north-easterly winds are dragging cold air straight out of the Arctic and Scandinavia for the next seven days, he said.
He added: "During the daytime, temperatures will struggle to rise much above freezing in some areas whilst, at night, the mercury will plunge to -5C or lower, giving hard and penetrating frosts. Snowfalls are expected quite widely, with eastern and northern parts of the country likely to be the worst affected."
Shoppers and office workers in the centre of London confronted with the sight of snowflakes on Wednesday were warned to expect another dusting in the coming days. The first wave of snow will affect East Anglia and south-east England through Thursday and Thursday night, with several centimetres likely in some areas, Mr Jones added.
Snow showers are expected in northern and eastern parts of the UK and these will continue into Friday.
"It is highly likely that most, if not all, parts of the UK will see at least a snow shower at some point in the next week," he added. "It is, perhaps, still a little early to say whether or not Christmas 2009 will be white or green. However, the prospects of seeing snow on the big day are greater than they have been for a number of years."
Bookies responded to the latest forecasts by cutting the odds of London experiencing a white Christmas from 8/1 to 5/2. William Hill said it would have to pay out millions of pounds if there is a blanket of snow across the country on December 25.
One gambler from Derbyshire stands to collect more than £14,000 if it snows on Christmas Day. Rupert Adams, spokesman for William Hill, said: "The million pound snow flake is something that we have always talked about in hushed tones and for the first time this millennium it looks like we could get collared. There is unlikely to be much festive cheer in our office this year."
