The very raw Arctic air returns South to all parts on Monday, on a freshening and blustery North wind. "But the wind chill is going to make it feel sub-zero".
Snow and ice covering the country may cause unsafe driving conditions and is likely to cause chaos on United Kingdom roads.
Road, rail, air and ferry services may be affected, while a loss of power in some areas is also possible.
Met Office meteorologist John West said: "We saw a fairly consistent stream of snow showers overnight, and there will be a constant feed throughout the day and into Friday".
Caroline, the third named storm of the year, is also expected to cause power cuts and bring large waves to coastal routes, seafronts and coastal communities in northern Scotland.
Winds are forecast to strengthen across parts of Britain on Wednesday ahead of the arrival of Storm Caroline.
Some parts of the United Kingdom have already woken up to a blanket of snow today.
About 8cm (3.1in) of snow had already fallen in Aviemore, in the Scottish Highlands, by dawn on Friday, while Antrim, Kinmel Bay, Leeds and areas to the west of the Pennines had also had a covering.More news: England Sevens beaten by Fiji in Cape Town
The Met Office says Storm Caroline's winds are now confined to the far north-east of mainland Scotland and the Northern Isles, and there could be gusts of 70-80 miles per hour at times, especially over Shetland, on Friday.
A yellow "be aware" weather warning is in place for the region, which runs from 8am on Thursday until just before midnight.
Parts of the West and East Midlands, the East of England, Yorkshire and the Humber and London and the South East could be affected.
East Anglia and the South East see outbreaks of rain, sleet and mostly hill snow, with wintry showers moving into districts bordering the East coast later.
'At the moment we have a yellow weather warning in place, but it could be upgraded to amber'.
Cold temperatures are likely to remain well into next week, with forecasters warning that Sunday could see further heavy snow showers.
"Road, rail and air travel delays are likely, as well as stranding of vehicles and public transport cancellations".
Highways England advised road users intending to travel through the West Midlands and the North West of England to check the forecast and road conditions before they travel, with the threat of disruption throughout the weekend.