The cold snap will continue for at least a week after temperatures dropped to -8C overnight.
Further weather warnings for snow and ice are likely to be issued by the Met Office later in the day.
Motorists are urged to defrost their cars, allow extra time for their journeys and drive carefully on slippery roads.
It comes after a double-decker bus overturned in “treacherous” freezing conditions in Somerset yesterday morning.
Meteorologist Tom Morgan said: “This is a cold spell lasting about five to seven days. I think if you live in Scotland or Northern Ireland at the weekend you will feel it getting a little milder – but it will remain cold in England and Wales.
“It may well not be until early next week for temperatures across England and Wales to return to normal.”
Up to 32cm of snow fell on Loch Glascarnoch in the Highlands yesterday and more is expected across the country today.
Amber snow and ice warnings are in place for most of Northern Ireland and parts of the North West, Midlands, Wales and South West until midday.
An ice warning covering much of the south expires at 10 a.m.
Driving conditions will be particularly difficult on the north and west coasts due to ‘stormy’ and ‘wintry’ showers.
Avon and Somerset Police urged people not to travel unless it was “absolutely necessary” and warned of “extremely icy and dangerous” roads.
Meanwhile, Cornwall Fire and Rescue Service said vehicles on the A39 at Trispen and the A391 at Bugle were stuck in snow.
It tweeted: “Be careful if you’re out and about today – snow has fallen in some areas and roads are likely to be icy. In built-up areas, pedestrians can take to the streets when sidewalks are dangerous.’
The RAC said there was a “big spike” in breakdowns on Tuesday due to icy conditions.
A spokesman said: “Although the weather is largely dry in most places, it is far busier today than yesterday, which is unusual as Monday is generally the day with the most breakdowns.
“Empty batteries are the number one reason why cars with older batteries finally give up the ghost in the cold.
“Ice and in some areas snow are the biggest risks for motorists this week – especially on untreated stretches of road.
“It’s important that everyone slows down and takes enough time to brake and react if something unexpected happens.”
The Met Office expects milder air to settle in Northern Ireland and Scotland from Friday afternoon.
Spokesman Oli Claydon said: “This will slowly spread to the rest of the UK. South East England will hold on to colder temperatures longer.’
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https://metro.co.uk/2023/01/18/met-office-warns-8c-cold-snap-to-last-for-another-week-18120312/ UK weather: Met Office warns cold snap of -8C will continue for a week