Parts of the north will continue to see "significant snow" over the next 24 hours and could experience the lowest overnight temperatures of the year, the Met Office has said.
The Met said that icy temperatures could even cause showery rain to fall as sleet or snow in parts of Wales and southern England, such as Wiltshire and Hampshire.
A number of yellow warnings for ice and snow are now in place across large areas of Scotland and Northern Ireland and stretch down into North Yorkshire.
The coldest weather is still expected in north west Scotland overnight on Thursday where temperatures could drop to an icy minus 10C (14F).
— Met Office (@metoffice) December 3, 2020
Alex Burkill, meteorologist at the Met Office, said that the "most significant snow" was likely to fall in England, in Cumbria and the Pennines – where areas above 400m could see up to 10cm.
"That's a significant amount of snow especially this early in December," he said.
"The snowiest months are usually a bit later into winter, January and February and also it's very early in December at the moment."
Mr Burkill added that the conditions could "quite easily make it the coldest night of the year so far".
The previous coldest temperature this year was recorded at Balmoral, Scotland, in February, where the mercury dropped to minus 10.2C (13.6F).
The lowest UK temperatures overnight on Wednesday was minus 5.6C (22F) at Kinbrace in northern Scotland, but conditions are expected to continue to get colder.
Further down south the lowest recorded was 1.8C (35F) in Charlwood, Surrey, and temperatures are expected to stay just above freezing in southern areas overnight on Thursday.
The Met Office said the cold spell is expected to last until Friday but that the weekend would see brighter weather and even some sunshine.
It added that temperatures going into next week would be lower than the average annual temperature, which is usually around 7-9C (45-48F).