Plummeting temperatures have prompted public health chiefs to warn the elderly to keep their homes warm and have the flu jab.
The Met Office has warned winter has begun to bite after an unseasonably warm December, with large parts of the UK facing blasts of snow, ice and frost.
Yellow warnings for ice have been issued for Scotland, Northern Ireland and parts of north Wales and north-west England as the mercury falls below zero.
With temperatures reaching as low as -5C in parts overnight, much of Scotland woke to frosty conditions on Wednesday morning.
The cold front is set to remain into the weekend, with Scotland and northern England bearing the brunt of the wintry weather.
John Lee, a forecaster at MeteoGroup, said: “The showers mostly cleared away by daybreak and it will be cold and clear in most places. There will be a widespread frost and minimum temperatures overnight could get as low as minus 4C or 5C in Scotland.
“There will be snow across southern Scotland and northern England, which could be quite heavy at times, especially during the night.
“Over the next few days temperatures are unlikely to get much higher than 5C or 6C pretty much anywhere and we are likely to see more widespread frost.”
The cold snap is in sharp contrast to last month, which was both the wettest and warmest December on record, when temperatures averaged 7.9C (46.2F).