Arctic blasts are set to sweep the country this week, bringing up to 8in (20cm) of snow as winter tightens its grip for the season's first big chill.
Bitterly cold weather is forecast across Britain with the mercury plummeting to minus 9C (15.8F) in northern Scotland while maximum temperatures in the capital are unlikely to rise above 2C (36F).
Many regions have been warned to expect snow flurries as the cold weather takes hold.
But while freezing temperatures are set to last well into next week, forecasters suggested the biting conditions could abate later in the season.
Overall, the UK could see a milder winter owing to a particularly strong La Nina episode in the Pacific.
The cooling of the tropical seas has been known to affect weather patterns across the globe and might mean a warmer than average start to the new year.
Aisling Creevey, a forecaster with MeteoGroup, the weather division of the Press Association, said overnight temperatures would remain below freezing this week, hitting their lowest point at the weekend.
"It is going to be cold, cold, cold. Temperatures are dropping to below average everywhere and will struggle to rise during the day," she said.
"A northerly wind will bring wintery showers and snow, particularly to Scotland and coastal areas, and by Wednesday we will really be able to feel the difference across the country."
The lowest temperature is expected to be recorded in Aberdeenshire (minus 9C) while London will be spared the harshest weather with lows of minus 2C overnight and highs of 2C during the day.
The heaviest snowfalls are likely to be seen in north-east Scotland while Yorkshire, Lincolnshire and East Anglia could see "significant snow accumulations".
Those in the capital and eastern parts of the country were also warned to brace themselves as Arctic winds blow over.
But though forecasters said it was still too early to predict a white Christmas, bookmakers Coral have begun to slash their odds.
Aberdeen is now the 3-1 favourite (from 4-1), while the odds in Edinburgh have fallen to 5-1 (from 6-1), and are at 7-1 in London and Cardiff, where they previously stood at 8-1.
Forecaster Stephen Davenport said: "My feeling is that we are looking at a colder than average first half of the winter and the second half could be less cold."
But he said there were "too many conflicting signals" to be certain about the precise conditions for the season ahead.
"The La Nina episode is fairly strong but quite where it's going is another matter," he added.
"Very generally, 70% of strong La Nina events are associated with temperatures of a little above average."