Large parts of the UK will be blanketed with snow and ice as chilly Arctic air blows in a bitterly cold start to 2026.
Snowfall is forecast for all four countries on Friday or Saturday, with blizzard conditions and “thundersnow” expected in the Scottish Highlands.
The Met Office said up to 40cm (16in) of snow was possible on higher ground in northern Scotland, with 10cm-20cm in lower-lying areas.
The forecaster added it will be a cold start to Friday, with rain, sleet and hill snow in Wales and central England which will head southwards, followed by icy stretches.
Snow showers will persist in northern Scotland and it will be bright and frosty elsewhere, it said.
Revellers saw in the new year with sub-zero temperatures across large parts of Britain at midnight on Wednesday, dropping to -6.2C (20.8F) in Bournemouth and -2.5C in Cardiff.
The wintry conditions are forecast to continue for several days as a result of Arctic air moving across the UK from Scandinavia.
Forecasters said delays and cancellations to rail and air travel were likely, in addition to power cuts and disruption on the roads. Some rural communities could become cut off, the Met Office said on Thursday.
Ch Supt Scott McCarren, Police Scotland’s head of road policing, urged motorists to consider whether their journeys over the next few days were essential.
He said: “If you need to travel, please drive to the conditions, be prepared for delays and allow extra time for your journey.
“Please don’t drive through road closures. The decision to close roads is not taken lightly and is done for public safety.”
The northern part of Scotland, including large parts of the Highlands and the region around Aberdeen, is expected to have the heaviest snowfall into the weekend.
Met Office amber weather warnings are in place for those areas, meaning severe disruption is likely, while yellow warnings for snow and ice cover large parts of the Highlands, Northern Ireland, Wales and England.
The worst of the disruption is, however, expected to have cleared by early next week, when most schools are due to reopen and people return to work.
Health leaders have warned that the cold snap will place further “extraordinary pressure” on the NHS after an extremely busy winter.
The UK’s Health Security Agency has issued amber cold health alerts for every region of England, which are in place until 10am next Tuesday.
Dr Paul Coleman, a health protection consultant at the UKHSA, said: “The weather is forecast to be very cold across England over the coming few days.
“Low temperatures like these can have serious impacts on the health of some people, particularly older people and those with serious health conditions. Exposure to cold can lead to increased risk of heart attacks, strokes and chest infections.
“It is therefore really important, as the colder weather sets in, to check in on friends, family and neighbours that are most vulnerable.”
