A series of travel warnings are in place as up to 15cm of snow is expected to blanket parts of the UK.
Heavy snow is falling across Yorkshire, the North West and is expected in the East Midlands, with the Met Office warning of possible power cuts, travel delays and flight cancellations.
Glasgow Airport has re-started operations after they were suspended due to weather conditions.
Overnight temperatures dropped to -12.3C in Loch Glascarnoch in Scotland.
The ground across much of the country is icy, with previous snowfalls now frozen solid.
"Snow is falling on ice and it's creating treacherous conditions," said Sky's Frazer Maude, who is in York.
An amber warning for snow has been issued for northern England and is expected to remain in place until 11am, with a yellow warning issued for southern and eastern Scotland and the Midlands.
Accumulations of up to 10cm (4ins) are likely and up to 15cm (6ins) could fall over higher ground, the Met Office says.
"Potent, heavy showers with a chance of hail and thunder," are forecast across the country from South Wales to Greater London, the Met Office has said.
Wind speeds are expected to reach around 50mph in some places, and gusts could reach 70mph on the coast.
Cumbria Police warned Titter users that every route in the south of the north western county was affected by snow, with traffic on the M6 disrupted by the icy conditions.
Snow in West Yorkshire is causing significant problems, as is the wind and heavy rain in the south west of England.
A fallen tree on the A39 near Bideford in Devon has left the road partially blocked, and Devon and Cornwall Police have warned of flooding on the A3075 near Newquay.
Highways England issued a severe weather warning. It urged people to plan their journeys, monitor weather reports and to pack a snow kit of blankets, food, water and a shovel if they really need to travel.
It comes after a night which was expected to be the coldest of the year, as parts of Britain were hit by Arctic air.
"Travel delays on roads are likely, stranding some vehicles and passengers. Some delays and cancellations to rail and air travel are likely," the Met Office warned.
"There is a possibility that some rural communities could become temporarily cut off. Power cuts may also occur."
On Wednesday, cancellations and delays caused by bad weather caused chaos at various travel terminals.
Stansted temporarily closed its runway twice due to ice, resulting in 27 inbound and 27 outbound flights being cancelled.
Around 50 flights were also cancelled at Luton.
Roughly 300 passengers were left in the terminal at Stansted waiting to rebook flights on Wednesday evening after dozens of Ryanair services were cancelled, along with a number of easyJet flights.
Lana Briggs, who had flown into Stansted from Dublin, told Sky News her aircraft was held on the runway for an hour and she was not told when her luggage would be unloaded.
She said: "People are talking about it turning into a riot if we don't get more information. I'm sure it's not going to happen but it does feel pretty devastating at the moment. It's definitely tense."
Heavy snow also caused disruption on the roads.
More from UK
The RAC said it saw a 15-20% spike in call-outs on Wednesday compared with the same time last year.
An AA spokesman said it had dealt with 8,000 breakdowns by lunchtime, which was "significantly more than a normal Wednesday in winter".