Swathes of the country face another bout of icy, wintry showers, although most at risk will be Scotland and northern England.
Meteorological developments through the coming days will decide whether southern Britain dodges the next Arctic blast.
Jim Dale, meteorologist for British Weather Services, said: “The exciting thing about Christmas is that now the cold weather looks like coming back in through the front door, bringing a flood of cold down from the north.
“It is going to turn much colder, although it is still early to say how far south the cold air will reach.
“It could be that southern regions end up in a colder airmass dragged in by low pressure through Christmas Day.
“In terms of wintry showers, a band of rain, sleet and snow will track the leading edge of the front, and it is most likely that we see sleet of snow over Liverpool, Manchester, Leeds and Scotland.”
Mild weather will hold out through the next couple of days as warm air from the Atlantic Azores Islands and the Canary Islands push temperatures around 10C higher than average.
Bitter Arctic air will have reached northern England by Christmas Eve before it creeps through the festive weekend.
Mr Dale, author of “Weather Or Not?”, said: “At the moment we are in sub-tropical air and as the week goes on, we will move into cooler temperate air before cold Polar air returns at the end of the week.”
Some long-range forecasters predict heavy snow in parts over the festive season as Britain braces for another Arctic pasting.
Weather models reveal temperatures plunging below -10C, while snow charts show swathes of Scotland and northern England in the path of wintry downpours.
Exacta Weather forecaster James Madden said: “The theme going through Christmas is going to be cold and wintry.
“Temperatures will start to drop from around Thursday, and this will be the start of a colder period with snow becoming a risk from then on.
“Snow could become even more widespread as we head into Christmas Eve and Christmas Day.
“At the moment, projections show very snowy conditions across the northern half of the country through the second half of the week.”
With the looming threat of plunging temperatures, bookies have once again taken the axe to festive snow odds.
Coral is offering 1-3 on a White Christmas with Scotland and the north favourites and the capital longer at 2-1.
Spokesman John Hill said: “Our odds suggest there is a 75 percent chance of us having a White Christmas.
“Edinburgh, Glasgow and Newcastle are the most likely cities to get snow, however, we are not ruling out the white stuff coming down in London and Southampton.”
The coldest conditions will strike across northern Britain later this week while the far south hangs on to milder temperatures, according to the Met Office.
Deputy chief meteorologist Dan Harris said: “From mid-week we expect to see a north-south split develop with colder weather arriving in the north, while the south hangs onto the mild conditions.
“There are, however, large uncertainties concerning where the boundary between these two air masses will eventually end up, especially as we head into the Christmas weekend.
“Christmas Day will most likely be mild with a risk of rain or showers in places for the south, especially the far south, while any cold air and wintry conditions will most likely be confined to the north of the UK.”