Heavy snowfall could bring disruption to the UK later this week, with as much as 25cm possible in some areas.
Temperatures will drop over the course of the week, with a yellow warning for snow issued covering Northern Ireland and much of Wales, as well as northern and central England, the Met Office said.
Up to 2cm is widely possible at low levels, 2-5cm on ground above 200m, and as much as 15-25cm above 400m, along with a risk of icy conditions.
The warning runs from 6am on Thursday for 24 hours and stretches from Cumbria and the Scottish border down to Stoke-on-Trent and Nottinghamshire.
All of northern and central Wales, including the Isle of Anglesey, is included in the warning.
There is a risk of power cuts, travel delays and some rural communities becoming cut off, the forecaster said.
The snow will ease later in the day and may turn back to rain or drizzle, especially in the south and east.
Met Office deputy chief meteorologist Chris Almond said: “While the early part of this week will see some rain, at times heavy, gradually sinking southwards, there’s an increased signal for wintry hazards as we move through the week as cold air from the north moves over the UK.
“It’s from Thursday that the snow risk becomes more potentially impactful, as mild air attempts to move back in from the south, bumping into the cold air and increasing the chance of snow developing on the leading edge.
“While there are still lots of details to work out, the initial snow risk looks highest in northern England and Wales from Thursday.”
Towards the end of the warning period the snow will turn into sleet and rain from the south.
Further warnings for ice could be issued later in the week, as temperatures drop below average for this time of year, the forecaster added.