Snow and ice is expected to bring a second day of disruption to air and road travel in parts of the UK.
Met Office amber warnings of a possible risk to life are in place in south-west England, south-east and mid-Wales and the West Midlands all day, where 5-10 cm of snow is forecast to fall widely.
Heathrow, Gatwick, Stansted and Luton airports have advised passengers to check the latest flight information.
South Western Railways has cancelled some early services to test its tracks.
A spokesman said the company might need to run de-icing trains to clear routes before its timetable can resume.
Meanwhile, Lincolnshire Police said up to 35 vehicles were stuck overnight in snow drifts on the A158 near the town of Edlington.
BBC Weather presenter Ben Rich said a more persistent area of snow began to develop over south-eastern areas and the Midlands on Saturday afternoon and is starting to drift further west.
Amber warnings remain in place in north-west England, Yorkshire, the Midlands, London and the South East until 09:00 GMT.
Yellow "be aware" warnings for snow and ice affect much of the England and Wales, central and south-west Scotland and parts of Northern Ireland until Sunday evening.
On Saturday evening Greater Manchester Police's Traffic unit posted a photo of snow-covered roads at junction 22 of the M62, which includes the highest stretch of motorway in the UK.
More than 100 flights to and from Heathrow were cancelled on Saturday and the airport warned of the potential for more disruption.
"We've worked with our airlines to consolidate Sunday's flight schedule, moving passengers on to fewer flights," a spokesman said.
"Our teams will be working throughout the night to keep our runways and taxiways operational and we will be closely monitoring the weather forecasts with our on-site Met Office."
Gatwick said passengers should check the status of their flights and also allow extra time for their journey to the airport.
Gatwick’s airlines are intending to operate a normal schedule today. Due to forecasted adverse weather, please check the status of your flight with your airline before leaving for Gatwick. If travelling to the airport, passengers should also allow extra time for their journey.
— Gatwick Airport LGW (@Gatwick_Airport) March 18, 2018
End of Twitter post by @Gatwick_Airport
Richard Leonard, Highways England's head of road safety, said while gritters would be treating the roads "it is still important to drive to the conditions when snow is forecast".
The wintry snap dubbed the "mini beast from the east" brought the heaviest snow showers on Saturday to north-east England and the North Midlands, as well as parts of southern England – including Hampshire, Sussex and Kent.
Temperatures dipped to a low of -3.2C in Loftus, North Yorkshire, during the afternoon and strong winds made temperatures feel as cold as -7C or -8C for some.
The Met Office said the daytime high at Great Dun Fell, in Cumbria – at a height of 847 metres – reached -7.1C, but with wind gusts in excess of 85mph, there was a "feels like" temperature of -22C.
A cold spell nicknamed "the Beast from the East" saw much of the UK and Europe blanketed in snow at the start the month.