Temperatures are set to plummet below -8C (17.6F) in parts of the UK by the middle of the week, with the Met Office issuing a warning for heavy snow in Scotland.
An Arctic chill is expected to sweep the country, bringing with it below-average temperatures for the time of year as winter begins to bite, with easterly winds expected to shift to the north.
The Met Office has put a yellow snow warning in place for Wednesday, which it says may cause disruption to road, bus and train journeys.
UK weather: The latest Sky News forecast
Alex Burkill, Met Office meteorologist, said: “At the moment we have an easterly flow and as such our winds are coming from the east and that is a cold direction, and it is cold out.
“However, from Tuesday onwards we are going to get a northerly flow, so our winds coming from the north, that is Arctic air leading to our temperatures dropping even further as we go through this week.
“It’s going to turn even colder and feel even colder still, with temperatures well below average for the time of year, both by day and by night.”
‘Cold is going to be very widespread’
Mr Burkill added that temperatures overnight into Thursday would drop to -7C (19.4F) or -8C (17.6F), and maybe even colder.
“It looks like the cold is going to be very widespread, perhaps Northern Ireland and East Anglia won’t be that cold, maybe just a degree or two below freezing,” he said.
“Otherwise we are talking about several degrees below freezing across Scotland, Wales.”
He said much of England, including the South West, could also see exceptionally cold temperatures of -5C (23F) or -6C (21.2F).
“We have a snow warning across the northern half of Scotland for Wednesday and that is when the snow showers coming from the north will be most impactful,” Mr Birkall added.
“They will probably start on Tuesday, and we will see very significant snow in the north.”
Forecasters predict the cold weather could last a week, as the northerly flow will linger and there may be some showers, though it will be largely dry and cold.
Temperatures dropped to -3.8C (25.16F) at Drumnadrochit near Inverness on Saturday night, but temperatures should remain at around -2C (28.4F) at night in Scotland for the next few days.
It will be a few degrees above freezing for the rest of the country until the cold snap arrives on Wednesday.
Daytime temperatures are predicted to be around 8C (46.4F) or 9C (48.2F), dropping to 5C (41F) or 6C (42.8F) as the week progresses.