Cold air sweeping in from the Arctic is set to bring frosty conditions to the UK, with snow and sleet forecast in northern parts.
The chilly snap will bring an end to the largely mild start to autumn, with people advised to dig out their warm winter clothes over the weekend.
Even in southern parts, where temperatures are forecast to be around 7C (45F), the wind chill factor means it will feel several degrees cooler, forecasters said.
A yellow warning for snow and ice is in place for northern Scotland from 8pm on Friday, while another for ice takes effect in Northern Ireland from 1am on Saturday.
Forecasters warned of patchy ice and slush affecting some upland routes as well as rail and road disruption.
Snow may dust the tops of hills in the Pennines in northern England, Snowdonia in north-west Wales, the North York Moors, and across the Scottish Highlands.
Met Office meteorologist Aidan McGivern said: “Snow building up over the higher routes, some icy patches for the north of Scotland as well as Northern Ireland to watch out for first thing Saturday.
“It will be a fairly chilly start, with temperatures widely close to freezing and that means you’ll perhaps have to scrape your car windscreen and you’ll see a frost in place first thing.”