More snow is on the way, forecasters have warned, bringing icy and treacherous conditions to the roads.
Temperatures could dip to minus 12C (10.4F) in parts of Scotland, particularly in areas that have already seen some snowfall, the Met Office said.
London could see its second dusting of snow of the winter as the mercury plummets, while this year’s record of minus 10.8C (12.6F) is also likely to be broken.
Yellow weather warnings for ice are in place in north-western Scotland and the northern and western isles, alerting travellers to be wary of slippery roads.
A similar warning is in place for north-west England, south-west England, Wales, Yorkshire and Humber.
The Midlands, east of England, Greater London and the south of England should also beware of fog making driving on icy roads even more complicated on Thursday morning.
A yellow warning for snow is also in place across large swathes of England and is due to remain in place until late on Friday night.
Most of Scotland should also be prepared for snowfall.
Commuters are urged to check local forecasts and weather conditions before they travel.
Meteorologist Mark Wilson said: “Potentially we could be as low as minus 12 tonight over snow cover across Scotland.
“It will be exceptionally cold – what we need to beat at the moment is minus 10.8C. That was at Braemar on January 18.
“I think there is still a very good chance that could happen – obviously it’s not a complete dead cert but I think it’s more likely than not that we will get colder than that. Definitely that’s one to watch.
“Even away from that it’s going to be a cold night across the board – temperatures widely below freezing and a pretty widespread and severe frost for many.”
Mr Wilson said the Met Office still expected snow overnight into Thursday morning, but at this stage it was unclear where would see the most.
“Some areas of higher ground could see as much as 10cm of snow – possibly a bit more than that over the highest ground in Wales,” he said.
Even London could get in on the action.
Mr Wilson said: “There’s definitely the potential for some accumulations in London – it’s a tricky one but there’s a risk of a light covering at least for a time.”
He said elsewhere in the south east could potentially get a bit more snow coverage – particularly across higher ground.
The deepest snowfall recorded by the Met Office at 9am on Wednesday was 11cm at Tulloch Bridge in Inverness-shire.
Depths of 9cm were also recorded in Thomastown in Co Fermanagh and Spadeadam in Cumbria.
Manchester and Liverpool airports were brought to a standstill on Wednesday morning, although a full service had resumed at Liverpool by 2pm and one runway was also opened at Manchester by midday.
Several schools in the cities were also forced to close their doors because of the harsh conditions.
Councils have prepared for heavy snowfall, with more than 1.4 million tonnes of salt stockpiled, the Local Government Association said.