Forecasters said hail and snow would accumulate across huge areas of north-west England and Scotland, where temperatures plummeted to -6C (21F) in the early hours.
south-west England and Wales have seen icy patches build-up on untreated roads, with drivers warned to take extra care.
In Glossop, Derbyshire, the A6068 was closed overnight after a five-car pile-up in the snow.
Elsewhere, some drivers were forced to abandon their cars on the M66 in Manchester after becoming stranded due to the conditions.
A string of other roads have been closed off by the heavy snowfall.
Back in Derbyshire, the A54, the A57 Snake Pass and the A6024 were all blocked off by wintry weather this morning.
Travellers have been warned of longer journey times as roads and railway lines are hit by the winter snap.
In a yellow weather warning, the Met Office said: “Heavy hail and snow showers are expected during Monday morning and will lead to ice and snow accumulating on many surfaces.
“The showers will be heaviest and most frequent across parts of western and northern Scotland.
“Longer journey times by road, bus and train services are likely while some vehicles could become stranded. Ice is likely to form on untreated pavements, cycle paths and roads leading to some injuries from slips and falls.
“Power cuts may occur and other services, such as mobile phones, may be affected.”
And they warned people should watch out for ice in the south-west.
The Met Office said: “Icy patches are expected to form on untreated roads, pavements and cycle paths on Sunday night and Monday morning.
“This is likely to lead to some injuries from slips and falls.”
Forecaster Rachael Adshead said Monday may feel slightly less cold than Sunday, with wintry showers expected in the north and west.
Scotland, Northern Ireland and north-west England will see snow showers, while further south is more likely to see a mixture of rain, sleet and hail.
But Meteogroup said the weather chaos could spread elsewhere in the UK this week.
A band of rain, sleet and snow will push eastwards across Britain tomorrow, bringing gales to southern coasts of England.
Drier and brighter conditions will develop in western parts later on, but there will still be wintry showers for western Scotland.
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