Blizzards and snowdrifts threaten to disrupt rail services and motorways today as heavy snow and high winds make milder winters seem a distant memory.

From Scotland to the Midlands, snowfalls of up to 20 centimetres are expected to play havoc with travel arrangements, and even London can expect traces of snow among the rain.

Trains equipped with snowploughs have been placed on standby by rail operators to clear routes crossing the Pennines, where the heaviest conditions are expected. During the night, Network Rail was using special trains to spray warm deicer on mainline stretches of track on lines in the North West and North East.

Drivers setting out overnight or early today were being advised to travel with warm clothing and an emergency pack including food and water, boots, windscreen deicer and a shovel.

Helen Chivers, at the Met Office, said: “We are expecting the heaviest fall to be over the Pennines, the North York Moors, and the Cumbrian Fells, which could get anywhere between 10cm and 20cm of snow. And it will be drifting, because it will be accompanied by higher winds, and higher roads could well be quite badly affected by blizzards well into the rush hour.”

The Met Office is warning travellers that there is an 80 per cent chance of disruption to journeys in Scotland and northern England, and a 60 per cent chance in the Midlands, especially on the M6 and A1 roads.

Network Rail says that Trans-Pennine routes will be the worst affected by snowfall, and has been inspecting the line to ensure that heaters prevent the points from freezing.

Severe weather warnings have been issued for parts of the country as far south as Birmingham, and authorities in London and across the South have been warned that heavy rain could turn into brief spells of snow and ice during today’s rush hour. People who have become used to milder winters will be well advised to wrap up against temperatures that could fall as low as minus 10C (14F) in parts of Scotland, although the South Coast could reach 10C later in the day.

The cold weather, which has lasted two weeks, has felt unusually harsh after a series of mild Decembers.

The bookmakers are shortening the odds on a white Christmas, with William Hill offering 4-1 for London and Manchester and 2-1 for Glasgow and Edinburgh. It is also offering 20-1 the lowest temperature recorded in England (minus 26.1C) to be beaten this winter and 100-1 for the Thames to freeze over between Westminster and Tower Bridges.

However, to the dismay of children everywhere, teachers will not be kept at home by snowdrifts next week, as skies are expected to brighten, bringing temperatures of about 6C in the day, with frost overnight.

Snow is not expected to settle for long on higher ground in the South of England, but it will remain for several days in Scotland and the North of England. After the overnight snowfall, sunshine, scattered showers and lighter winds are expected.