Amber warnings are more serious than yellow warnings and indicate a possible risk to life due to severe weather, as well as more significant travel disruption.
Much of England and Wales is covered by a separate yellow warning for snow and freezing rain into Sunday, though there is uncertainty over how disruptive the adverse weather could be, with milder temperatures forecast.
Most of Northern Ireland, as well as an swathe of northern Scotland, are also covered by yellow warnings for snow and ice.
On Sunday, fresh yellow weather warnings will come into force in some areas.
Heavy rain and thawing snow could lead to flooding in some parts of north-west England and Wales, while localised snow and ice warnings cover parts of Scotland.
BBC Weather forecasts that 20-40cm (7.8-15.7in) of snow could fall across northern England and southern Scotland from late Saturday into Monday.
Wales and northern and central England are expected to see the most sustained period of snow and freezing rain, with 3-7cm of snow likely and around 15-30cm on higher ground.
Later on Sunday, temperatures are expected to be milder in parts of the country, reaching 13C in London in contrast to Aberdeen where it could be just 2C.
