Up to four inches (10cm) of snow is expected to fall in parts of England and Wales overnight raising fears of widespread disruption to the roads and railways.
Forecasters said the freezing weather was set to continue for the next few days, with temperatures expected to plummet to -8C (18F) over the weekend.
And charities have warned that elderly people are among the most vulnerable in the freezing conditions.
Age UK director general Michelle Mitchell said more than a third of over-65s fall each year, with snow and ice posing a particular risk. She said: "We would encourage people to be good neighbours and clear pathways of snow and ice, if they are able to help older people stay safe."
A spokesman for the Association of Train Operating Companies (ATOC) said train companies were gearing up to deal with the bad weather, with Network Rail running empty 'ghost' trains and de-icer units to keep tracks and overhead cables free of snow and ice as far as possible.
He added: "The whole industry will be working hard to get people from A to B as quickly and reliably as possible."
Martin Young, chief forecaster at the Met Office, said: "We are expecting some snow across parts of the country overnight and into Friday.
"Whilst there is uncertainty about where the heaviest snow will be, we expect a covering of 1cm to 5cm of snow in many areas and possibly up to 10cm in the worst affected regions of perhaps the Midlands and south-east Wales. As a result there could be some disruption to travel."
Chris Burton, forecaster at MeteoGroup, the weather division of the Press Association, said snow was forecast to fall in Yorkshire, the Midlands, central southern England, western parts of East Anglia and London.
He said: "Tomorrow, with cloudy skies, temperatures won't drop too low but it will be generally freezing across most of England with lows of -1C (30F) or -2C (28F). It will struggle to get above freezing in parts of East Anglia but it will get up to 1C (34F) or 2C (36F) in England."
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