An ice alert for the South East and West Midlands is among new weather warnings now in force across the UK.
Wintry conditions caused widespread travel problems on Tuesday and forced more than 200 schools to close.
Forecasters say the difficult conditions will last until Wednesday morning, raising the prospect of a tricky rush hour on the roads and public transport.
The ice alert covers London and most of southern England as far west as Exeter, and as far north as Birmingham, Leicester and Chester, and expires at 10am.
A snow and ice warning also covers nearly all of Wales apart from some far western areas, most of western and northern Scotland and all of Northern Ireland – again until 10am.
Another snow and ice warning snakes up the east coast from Norfolk to the Scottish border and is in force until noon.
The Met Office has warned some journeys by road and rail could take longer in the morning.
It says drivers should allow extra time and pack items such as a blanket, spade, phone charger, and food and water.
Walkers should also be wary of icy surfaces and cyclists are advised to stick to main roads that are more likely to have been treated.
Temperatures in many places are set to be close to or below zero overnight, while snow accumulations are forecast to range from a couple of centimetres to potentially 10cm or more on higher ground.
Areas above 300m in Scotland could see build-ups of 15-20cm, the Met Office said.
Check the forecast in your area
The Met Office’s chief meteorologist, Neil Armstrong, said: “With cold Arctic air firmly in place over the UK, continued winter hazards are likely through much of this week, with further updates to warnings likely in the coming days.”
Monday night saw sub-zero temperatures for much of the UK, reaching as low as -11.2C at Braemar, Aberdeenshire.
Snowfall was also widely reported, with 12cm recorded at Watnall in Nottinghamshire on Tuesday morning.
By Tuesday afternoon, around 140 school closures had been reported in Wales, around 50 in the West Midlands and 20 in Derbyshire.
There was also a travel headache for thousands of train passengers as National Rail warned of disruption to various routes.
By midday, around 64 of 120 services (53%) planned by East Midlands Railway had been cancelled or delayed by at least half an hour, according to punctuality website trains.im.
Figures for other operators included London North Eastern Railway (37%), Transport for Wales (13%), West Midlands Trains (13%) and CrossCountry (12%).
Rail travellers have been advised to check online before setting out and drivers should also plan ahead.
Darren Clark, from National Highways, said: “Gritters will be out treating our roads around the clock when ice or snow is forecast, but it is still important to drive to the conditions.
“Keep your distance and reduce your speed, because even in conditions that seem normal, and where the snow is not settling, it can be slippery if ice patches have formed, or where fresh grit has not been worked into the carriageway.
“Drivers should plan their journeys, monitor weather reports and pack a snow kit of blankets, food, water and a shovel.”
The first amber cold health alert of the season has also been issued by the UK Health Security Agency (UKHSA) covering all of England, except the South, until 6pm on Saturday.
The amber warning is issued when the weather is likely to “cause significant impacts across health and social care services”, including the potential for a rise in deaths, particularly among older people or those with health conditions.
Dr Agostinho Sousa, head of extreme events at the UKHSA, said: “It is vital to check in on vulnerable friends, family and neighbours to ensure they are well prepared for the onset of cold weather. Particularly if they are elderly or otherwise at increased risk.”
Yellow health alerts – the second lowest – are in place for the South East, South West and London.
More expected in coming days
The Met Office has warned there could be further heavy rain, strong wind and more snow during the rest of the week as temperatures stay below average
“Further snow accumulations are expected through the week, mostly by night at low levels, in northern Scotland and exposed parts elsewhere,” it said.
Those in the impacted areas have been told power cuts are possible and mobile phone coverage might be affected.
The Met Office said there was also a slight chance some rural communities could be cut off.
