A cold weather alert, covering most of England, begins this morning ahead of an Arctic chill set to sweep across the UK.
The warning from the UK Health Security Agency (UKHSA) comes into effect between 9am on Sunday and 9am on Thursday.
The Met Office has issued two separate yellow warnings for snow and ice – the first is in northern Scotland from 4pm on Sunday until 11am on Monday. Up to 10cm (4in) is possible on higher ground.
Check the forecast in your area
A second yellow warning from 10am on Monday applies for 24 hours and covers parts of northern England and southern Scotland.
Up to 20cm (8in) of snow is possible on higher ground and 10cm (4in) at lower levels.
For several days forecasters have been predicting a cold front will move in across the UK, but until now there has been uncertainty about the probability and impact of snow.
Met Office meteorologist Ellie Glaiyser said Sunday may start chilly with temperatures not rising much above 4-5C (39-41F) across northern parts of Scotland with plenty of showers predicted in the afternoon.
That contrasts with 11-12C (52-53F) in the far south of England where brighter spells are expected.
But by Monday morning there is a chance of rush-hour disruption with temperatures forecast to drop to zero “if not just below” especially in rural areas.
In the north there could be “quite a hard frost” which “could lead to some icy stretches”, she said.
Monday’s yellow weather warning covers an area from Huddersfield in northern England as far north as Stirling in Scotland.
The Met Office is forecasting sleet and snow is most likely to fall over higher ground such as the Pennines.
It warns there is a small chance of power cuts, disruption to bus and train services, and travel delays for drivers on the roads.
“We could see some sleet and snow perhaps causing some disruption during Monday afternoon to lower levels,” she said, but added that sleet and snow is mostly likely to be isolated to parts of Scotland.
Meanwhile a separate UKHSA yellow alert – ranking as the second lowest of four alert levels – is in force for the next few days. It covers a large area of England, north of Northhampton.
It is triggered when there is a risk that healthcare services might face extra pressure and is designed to prepare those who are “particularly vulnerable” and “likely to struggle to cope”.