The Met Office has issued a raft of new snow and ice warnings with most of the UK hit tonight or tomorrow.
Yellow weather warnings have been issued for snow in London and the South East, North East, Yorkshire and the Humber, the South West, Wales, West Midlands, the Highlands and the Grampians, with all likely to be affected tomorrow and on New Year's Eve.
And the West Midlands, and parts of Scotland, Wales and Northern Ireland have been hit with yellow snow and ice warnings from today into tomorrow.
Roads and travel are likely to be affected with longer journey times, as well as icy patches on untreated roads, pavements and cycle paths.
The Met Office also warns that people may suffer injuries from slips and falls on icy surfaces too.
Meteorologists say showers will affect parts of the north Wales on Tuesday evening, then parts of northwest England and the northwest Midlands overnight.
As temperatures fall below freezing some ice is likely to form on untreated surfaces. Showers may be wintry on high ground with 1-3 cm snow settling above 300 metres.
Bands of rain, sleet and snow were moving across the UK this morning, bringing dangerous driving conditions, particularly around Manchester, Gloucestershire, Wiltshire and Berkshire, the Met Office said.
Temperatures plunged as low as minus 7.7C (18F) near Inverness in Scotland on Monday night, while nearby Aviemore saw 9cm of snow and Lake Vyrnwy in Powys, Wales, had 7cm, it added.
Met Office meteorologist Alex Burkill said the agency lacks a comprehensive ability to measure snow depth and anecdotal reports online of 5cm to 10cm of snow across many parts of the UK were likely to be accurate.
In east Lancashire, there were "lots of collisions coming in as the snow falls heavily", according to Deputy Chief Constable Terry Woods, while Highways England also warned motorists over snow-hit roads.
Snow caused some supermarket delivery orders to be cancelled, with Tesco saying it was unable to reach some customers in Stoke and the West Midlands.
A yellow warning for snow and ice for much of England, Wales and Scotland was in force until 10am on Tuesday after heavy snow in some regions, with more wintry weather expected on Wednesday and Thursday.
Freezing fog patches are likely to be slow to clear in parts of England and western Scotland, the Met Office added.
Fresh warnings are likely to be issued throughout the day, including one for snow and ice across swathes of Scotland and Northern Ireland for snow and ice on Tuesday evening, Mr Burkill added.
He said there was also a risk of rain turning to ice in North Wales and north-west England, particularly around Cheshire, overnight into Wednesday as temperatures plunge below freezing.
Temperatures in the afternoon are forecast to be around 4C-7C across the UK, turning cold quickly in the evening with a widespread frost.
The Met Office said: "Wintry showers will start to fade inland in the afternoon, but they will continue to stream into coastal areas, northern Scotland and Northern Ireland."
Mr Burkill said coastal areas could also see hail and thunder.
Southern parts of England have been warned there is a chance snow and ice could hit on Wednesday and Thursday.
Mr Burkill added: "The amount of snow would be disruptive and impactful. We could still see a few centimetres building up. These areas don't usually see that much snow."
A low pressure system will see rain meet cold air, turning to snow over hills and lower areas.
The cold snap is forecast to continue well into the new year.
