Heavy snow has fallen across the west of England following an amber weather warning from the Met Office - and is headed eastwards.
The freezing temperatures have led to weather warnings being issued by the Met Office for snow, ice and fog into Friday.
There are warnings of rail delays and cancellations, power outages and the cutting off of rural communities.
Around 100 cars became stuck on the A30 near Temple in Cornwall because of a whiteout - while snow depths of 12cm has been recorded in Bodmin in the county.
The latest weather warnings:
Yellow snow and ice warnings in place for a wider area across southern England and Wales and for the east of the UK and northern Scotland.
The areas in England that will be most affected by the warning - which is to remain in place until late on Friday night - are Hampshire, Bath, Bournemouth, Bristol, Devon, Dorset, Gloucestershire, Somerset and Wiltshire.
In Wales, the warning is for Blanenau Gwent, Bridgend, Caerphilly, Cardiff, Merthyr Tydfil, Monmouthshire, Neath Port Talbot, Newport, Powys, Rhondda Cynon Taf, Torfaen and the Vale of Glamorgan.
Warnings for ice are in place in north-western Scotland and the Northern and Western Isles, alerting travellers to be wary of slippery roads.
The Met Office's amber weather warning - which means a risk to life and property, as well as the potential for travel delays and interruption to power supplies - across the west of England ended at 9pm on Thursday.
The latest travel disruption details:
Highways England, which urged motorists to "take care when driving", said key routes affected include the A30, the A38 and the M5.
Gritters have been out on the roads, with snowploughs, vehicles and more than 60 staff on standby in Somerset, where the country council has urged people to look after vulnerable friends, family and neighbours.
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.
South Western Railway has warned passengers trains may be cancelled on Friday morning while work is done to check and clear the tracks.
David Dickson, chief operating officer for Network Rail's Wessex Route, said: "With snow and freezing conditions expected, we are asking passengers to please check before they travel (on Friday) morning."
Southeastern Trains said it would run its “winter weather timetable” on Friday due to the forecast.
'We're not just travelling because we want to, we're travelling because we need to'
An "intensive effort" was launched to help the motorists trapped on the A30 near Temple, according to Chief Inspector Adrian Leisk, head of roads policing across Devon, Cornwall and Dorset.
A plough and a gritter were sent to help the drivers who are backed up along the snow-coated carriageway, according to images on social media.
Devon and Cornwall Police tweeted: "We are working hard with partners to clear the stranded vehicles on the #A30 at #Bodmin. @HighwaysSWEST gritters are on scene now. If you are stuck please stay in your vehicle and keep as warm as possible. We will get to you as soon as we can."
Snow 12cm deep was measured on Bodmin Moor in Cornwall, according to the Met Office.
There is 5cm of snow in Sennybridge, Powys, 8cm in Spadeadam, Cumbria, and 7cm in Tulloch Bridge, Inverness-shire, the forecaster added.
Grace Pascoe in Truro
Temperatures set to stay low after midweek plunge
The ongoing weather warnings come after temperatures dropped to their lowest in the UK so far this winter.
The Met Office announced late Thursday that Braemar had fallen to -14.5C, colder than the previous night's temperatures.
Loch Glascarnoch in the Scottish Highlands was the coldest spot in the country overnight Wednesday as temperatures dipped to -13.6C, 2.8C lower than the previous record for 2019.
All four countries in the UK set new records for the 2018/2019 winter on Thursday, with Sennybridge, Powys, dropping to -9.3C, Katesbridge in Northern Ireland falling to -8.2C and Redesdale Camp, Northumberland, recording temperatures of -10.5C.
Met Office forecaster Mark Wilson said the cold temperatures were due to stick around.
He said: "On Thursday night we could see similar temperatures in Scotland, but Northern Ireland, England and Wales probably won’t be quite as cold. Saturday night into Sunday could also be very cold."
Drone footage of conditions in Oxfordshire