Heavy snow, gales and freezing rain are set to blast large swathes of the country this weekend.
Forecasters stepped up weather warnings as Storm Deirdre is expected to bring widespread travel disruption and power cuts.
Six yellow and amber weather warnings cover almost the entire UK, apart from London and the south east, which are still expected to see heavy rain.
Up to 40cm of snow could fall over high ground in Scotland and around 10cm on flatter parts.
A new amber alert issued on Saturday warns of freezing rain and a "prolonged" period of heavy snow developing in the Scottish Borders in the afternoon.
Another amber warning predicts potential blizzard conditions bringing disruption to transport and infrastructure in central and Northern Scotland between Saturday and Sunday mornings.
A third amber alert anticipates widespread freezing rain hitting the country from the southern Pennines up to central Scotland.
The Met Office warned that the "rare" weather phenomenon poses a "danger to life" and risk of injury as it creates very slippery surfaces.
Met Eireann, the Irish weather service, named an area of westwards-moving low pressure Storm Deirdre on Friday night.
It has issued an orange alert for the entirety of Ireland, warning of wind gusts up to 80mph and persistent and heavy rain.
For the UK, the Met Office has issued a series of warnings stretching from Land's End to the Shetland Islands.
It said pavements and cycle paths are likely to become instantly impassable because of the sudden formation of black ice.
This will also create dangerous driving conditions and is likely to lead to road traffic collisions, road closures and longer journey times.
Freezing rain is expected to strike from around lunchtime on Saturday and last until early Sunday.
A yellow warning of heavy rain and strong winds up to 70mph is in place for Northern Ireland, south-west England and South Wales until 6pm on Saturday.
Winds of between 40mph and 50mph were beginning to be be recorded in the region early on Saturday morning.
A further yellow warning of snow and ice that covers nearly all of England and Scotland will run for 24 hours from 9am on Saturday.
A yellow warning of severe gales has been issued for Northern Isles and parts of Caithness.
Met Office forecaster Simon Partridge told the Press Association: "If you're not under a snow and ice warning you're probably under a wind and rain warning.
"The good thing is that Deirdre is expected to clear out the cold air and become much milder across the weekend."
Freezing rain, a "rare" weather event for the UK, is forecast from the southern Pennines up to central Scotland.
"The problem is it freezes instantly on contact with cold surfaces, covering them with hard, clear ice," Mr Partridge said.
"That means power cables can be covered and supplies can be interrupted if they are brought down by the ice.
"There can also be issues with untreated roads."
Additional reporting by Press Association.
