Temperatures dropped to nearly minus 10C on Monday night – the coldest of the autumn so far.
According to the Met Office, the mercury fell to minus 9.9C (14.2F) in Braemar, north-east Scotland, on Monday night.
Nine of the 10 coldest locations overnight were in Scotland.
A yellow weather warning for dense and freezing fog was in place across large parts of the UK.
READ MORE: Scotland's weather: Temperatures plunge to -8C as UK heads for coldest night so far
According to the Met Office, the freezing fog will “linger” across many parts of the country throughout the day.
Meteorologist Grahame Madge said: “It’s going to clear, but it might be stubborn to clear in some places, and then eager to re-form.
“We have weather warnings out until 11am (on Tuesday) but in some places it could persist more than that.”
The freezing fog hung around throughout Tuesday morning’s rush-hour.
North West Motorway Police tweeted to say they had received reports of a “few” accidents, adding: “the gritters have worked tirelessly all night, but it’s still icy out there.”
They also offered some safety tips for motorists, suggesting people drive on main roads, rather than quieter rural routes, and use a cigarette lighter to warm a key if the locks are frozen.
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Mr Madge said: “Fog is always a driving hazard, and people need to take account of that when they are travelling.”
He warned drivers not to become complacent if they have passed through a clear area, saying “Don’t think the next 10 miles will be free of fog.”
Temperatures throughout the day will struggle to reach double figures across much of the country.
Southampton is predicted a maximum high of 10C-11C (50F-51.8F), but only 8C (46.4F) is expected in London, 6C-8C (42.8F-46.4F) in Norwich, 5C-7C (41F-44.6F) in Nottingham, and 4C-5C (39.2F-41F) in Aberdeen.
Temperatures will fall again overnight on Tuesday, but Mr Madge could not say “whether they will drop to the levels they did last night”.
He added: “We have a weather front moving in from the west that’s going to stall and bring cloud and rain.
“But for the east the cold conditions are going to persist.”
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