Following upgraded weather warnings from the Met Office, snow and ice are expected across parts of the UK over the weekend and into next week.
The worst conditions are expected in Scotland, where an amber warning for snow came into effect on Friday afternoon. Yellow warnings for snow and ice remain in place for other areas until Monday.
Up to 40cm (15 inches) of snow could fall in parts of Scotland on Friday, while the Met Office is forecasting up to 5cm in parts of England and Wales.
The weather service said the wintry weather is expected to cause delays and cancellations to rail and air travel, road closures and power cuts.
A yellow warning for snow and ice was issued on Thursday midnight for large parts of England, Northern Ireland, Wales and Scotland.
Different parts of the UK will be affected at different times over the weekend, with a full list of affected areas available from the Met Office.
Most of the warnings were initially due to expire on Saturday, but the Met Office has issued a new wave of alerts, which will run until Monday.
The amber warning in Scotland is currently in effect until Saturday afternoon.
Areas expected to be affected by "blizzard conditions" include Angus, Perth and Kinross, Grampian, Aberdeenshire, Moray and parts of the Highlands. The Met Office has warned that power cuts and vehicles becoming stranded are likely in these areas.
With names like Sir Andy Flurry, Robert Burns and Plougher O'Scotland, the Scottish gritter and snowplough fleet is working at full capacity on the country's road network.
Meanwhile, National Highways said there have been several accidents in Derbyshire, Leicestershire and Nottinghamshire, and motorists have been advised to use alternative routes where possible. People are being urged to plan their journeys carefully and carry essential supplies in their cars in case of delays. Essential items to bring with you include warm clothing, water, blankets, and an ice scraper.
Cold Arctic air is sweeping across the UK, bringing temperatures well below average and increasing the risk of snow and ice.
Met Office meteorologist Neil Armstrong has predicted that this cold spell "could last into next week" and that "winter hazards will remain and further weather warnings are likely to be issued." Health Secretary Wes Streeting has warned that the "very cold weather" will put extra pressure on NHS hospitals and has urged people to only go to A&E in emergencies.
According to the UK Health Security Agency, the anticipated temperatures could have a serious impact on some people's health, increasing the risk of heart attacks, strokes, and chest infections, particularly for those over 65 and those with pre-existing health conditions.
The icy conditions also increase the risk of falls.
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