Extreme weather left drivers stranded and more roads impassable overnight - with another day of sub-zero temperatures, icy blasts and "blizzard-like" conditions to come.
Storm Emma, rolling in from the Atlantic, looks poised to meet the Beast from the East's chilly Russia air - causing further widespread snowfall and bitter temperatures.
As winds picked up overnight, drifting snow caused misery for many motorists - with some parts recording accumulations up to a foot deep.
In Lincolnshire, police said the A52 had become impassable between Boston and Skegness, and warned that officers would not be able to rescue stuck drivers.
Not even a snowplough was able to get through, the fire service said.
There was also misery for drivers in Scotland - where the highest level of weather warning, a red alert, remains in place until 10am today.
Motorists on the M80 near Glasgow reported being stuck for up to 13 hours, with some spending the night in their cars, and others abandoning their vehicles on the motorway.
Please find the latest statement from Glasgow Airport below. If you are a passenger in the terminal, please find a list of food outlets located before security that will remain open here: https://t.co/XRhvbZjXk5 pic.twitter.com/dwXvTcTpOa— Glasgow Airport (@GLA_Airport) February 28, 2018
Temperatures plunged to a widespread low of between minus 6C (21F) and minus 4C (25F) overnight, and forecasters have warned it could feel as chilly as minus 11C (52F) during the day as the winds continue to strengthen.
Gusts of up to 60mph could also bring "blizzard-like conditions".
As well as the red alert - which has never before been issued for Scotland, England or Northern Ireland - amber warnings have also been issued for the north-east of England and the central belt of Scotland, in place between 10am and 8pm on Thursday, and for south west England and south Wales from 12pm until 8am on Friday.
On top of these, yellow snow warnings have been issued for vast swathes of southern, central, and northern England, Northern Ireland and Wales - in place for most of Thursday.
Met Office forecaster Simon Partridge said some parts of the south west could see up to 50cm of snow by Friday morning.
If you're travelling today a reminder to drive with extra care, @metoffice have issued several warnings for snow this week, For the latest info visit https://t.co/zS1Zan6TfW ... #BeastFromTheEast pic.twitter.com/1keiaYkr8G— Highways England (@HighwaysEngland) March 1, 2018
"If you don't have to go anywhere over the next few days, stay at home," he warned.
Met Eireann, the Irish meteorological service warned of blizzards, severe thunderstorms and coastal flooding after issuing a red alert for the whole of the country.
In response to the impending heavy snow showers all schools, community centres and libraries in Edinburgh will be closed, the city's local authority said.
Plymouth Council said more than 80 schools would be closed on Thursday, with more than 50 in Newcastle and 103 across Devon remaining shut.
Disruption across the country's road and rail network is expected to ensue throughout rush hour on Thursday, with road closures already in place and alterations to train services.
Several airports reported disruption due to the weather, with Gatwick Airport expecting "a large number of cancellations and delays to flights".
Due to severe weather, we are expecting a large number of cancellations and delays to flights today. Please check the status of your flight with your airline before leaving for Gatwick and do not travel to the airport if it is cancelled. Please allow extra time for your journey.— Gatwick Airport LGW (@Gatwick_Airport) March 1, 2018
Glasgow Airport said there would be no flights until 11am, while Edinburgh Airport tweeted to say most airlines had cancelled flights from there until lunchtime.
The extreme weather shows no sign of letting up, with fears snow in the south west could turn into freezing rain on Friday - making conditions "even more treacherous".