Motorists have been warned of "potentially fatal" conditions on the roads due to the heavy snow, which also caused flight cancellations and delays at Britain's busiest airports.
The warning from motoring organisations comes as many drivers hope to make an early start to their Christmas holidays.
However, freezing conditions led to travel chaos with those hoping for a Christmas getaway finding themselves stranded at airports, with hundreds spending the night in terminals as planes were grounded.
Temperatures dropped overnight on Sunday, with Castlederg, County Tyrone, in Northern Ireland recording a fall in mercury to minus 17.6C - a record low for the region.
Chesham in Buckinghamshire is thought to have recorded the lowest UK temperature overnight at minus 19.6C.
Weather forecasters have predicted that the sub-zero temperatures will continue with snowfalls of up to 20cm expected on Monday.
Aisling Creevey, a forecaster with MeteoGroup, the weather division of the Press Association, said: "There are temperatures of minus 14 and minus 15 quite widely across the UK, with no let-up in sight.
"We will be seeing figures like this over the next night or two, with significant snowfalls forecast for Wednesday."
Those hoping for a white Christmas may be disappointed however - with the weather for Christmas Day itself set to be "wet and windy", she said.
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