Heavy snow bend travels east through southern England and Wales, leading to serious road disturbances and leaving 100 drivers stuck on the roads in Cornwall.
In the parts of the country, up to 10 cm of snow is expected, and winter rains are expected later in London.
British Airways warned that unfavorable weather conditions would "probably affect" some short-haul flights, while Transport for London advised travelers to complete their travels until 21:00.
The Office released a yellow warning about life threats, mainly covering parts of southwestern and southern Wales, which lasts until Thursday at 9 pm.
"Intense efforts" are underway to help the drivers who captured the A30 engine after escaping to Cornwall, officials said this evening.
Meanwhile, a multi-vehicle collision closed M6 near Wigan.
The Information Office warned of road delays, jammed vehicles, traffic jams and cancellations, power cuts and rural communities.
5cm snow depths were recorded in Bodmin, Cornwall and Sennybridge Village in Powys, prognosticists said.
Met Office also reported snow in Wiltshire, Hampshire, Sussex and Kent.
Cornwall Airport, near Newquay, was forced to temporarily close on Thursday.
Engines in England said the plows and spreaders were sent to assist drivers in Cornwall and warned people not to travel after the "significant" snow.
Chief Inspector Adrian Leisk, chief of traffic police across Devon, Cornwall, and Dorset, twitched: "For those stuck at the A30 in Cornwall, intense efforts are being made to clean the car guides to allow bullets.
"Please stay with the car and we will come to you."
In addition to amber warnings, there are yellow and ice warnings in the wider area of southern England and Wales, and in the east of Great Britain and Northern Scotland.
M6 is closed in the north direction between the joints 25 and 26.
Motorways in England tweeted: "Traffic officials are on the scene and all emergency services are on their way."
The Southwest Railways warned passengers that trains might be canceled tomorrow morning while work is being done to check and clean the rails.
David Dickson, Chief Operating Officer for Wessex Network Rail Rail, said: "With regard to the expected snow and freezing, we ask the passengers to test before tomorrow morning."
Metastas predictor Steven Keates told the Standard: "What we saw so far is the rain band that turns into snow as it pushes toward the east.
"Some people had already hit Newquay, and there was a lot of snow on the A30. Cornwall, Devon, Somerset and South Wales were the worst hit.
"There is a mixture of rain, sleet and snow, but rain could quickly turn into snow.
"The conditions have the potential to become quite inconvenient as we move toward the hourly crowd when they will hit Taunton and Bristol, Cardiff and Newport.
"A 10cm snow can fall in places during the evening hour of lively traffic so it can cause maximum disturbance.
Later this evening the weather will move eastward to Southampton, Bournemouth, Brighton, and then to London.
"Tomorrow morning we could see one or two transport problems in the capital."
Weather warnings were issued after the country had so far the coldest night of winter.
The coolest place overnight was Braemar in Aberdeenshire, where mercury fell to -12.9 degrees, and temperatures continued to fall on Thursday morning, with the lowest -14.4 degrees.
On Wednesday evening, all four parts of the UK set new winter records with Sennybridge in Powys, Wales, falling to -9.3C; Katesbridge in Northern Ireland fell to -8.2C; and a Redesdale camp in Northumberland that records temperatures of -10.5C.
The areas most affected by the warning in England 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 Vale of Glamorgan.
The Target Office said: "Snow sometimes could be difficult and about 3 to 7 inches could calm down within two to three hours and in some places up to 10 cm.
"Most snowballs are likely to be in areas over 150 meters."
Sprayers were on the road, with snow plows, vehicles, and more than 60 people in the state of alert in Somerset, where the Council of Nations urged people to take care of vulnerable friends, families and neighbors.
Engines in England, which pushed drivers to "take care of driving," said the key routes affected by the A30, A38 and M5.
Police in Wiltshire reported that the Press Office said "we expect rain to turn into snow, especially on hills, turning into ice conditions."
The forces added, "Since last year, we know how to be in the snow and ice conditions, especially on our road networks.
"So in the real British way, we hope the best, but we are preparing for the worst."