From Tyneside to Buckinghamshire, snow fell across the much of the country on Tuesday as forecasters warned temperatures could plunge to a 2023 record low of -15C in some parts.
The Met Office says the mercury could dip to the lowest of the year so far in some sheltered Scottish glens, especially where there is fresh snow cover.
Warnings for snow and ice are in place across the UK and more are expected to be issued as Arctic air sweeps through the country.
The lowest temperature recorded in the UK so far this year is -10.4C, at Drumnadrochit near Inverness in the Highlands in the early hours of 19 January.
On Tuesday morning, people were waking up to snow across Scotland, Northumberland, Tyne and Wear, Yorkshire, Bedfordshire and Buckinghamshire.
Temperatures are forecast to drop almost 6C below their coldest last March, when they reached -9.1C in Aboyne, Aberdeenshire.
The Met Office confirmed the coldest temperature in the UK overnight on Monday into Tuesday was recorded as -7.6C at Altnaharra in Sutherland, Scotland. The lowest temperature in England over the same period was -7.1C at Shap in Cumbria. In Wales it was -0.9C at Lake Vyrnwy in Powys and in Northern Ireland it was -5C in Antrim.
A yellow weather warning for snow and ice will be in place for London, the Thames Valley, East Anglia, parts of the Midlands and south Wales until 10am on Tuesday.
An identical one will be in place in Northern Ireland at the same time. A yellow weather warning for snow and ice is in place in much of northern and eastern Scotland and north-east England.
The area covered by it is likely to extend as far south as Hull from Tuesday before it lifts at about 10am on Wednesday.
South-west England and south Wales will be covered by a yellow warning for snow all day on Wednesday, and a few centimetres of snow could fall in those areas.
Northern England, north Wales, most of Scotland and Northern Ireland will be covered by a yellow warning for snow between 3am on Thursday and 6pm on Friday.
The Met Office spokesperson Grahame Madge said: “Temperatures will be much, much colder than we would expect at this time of year. The pattern will set in for some time. We have got this feed of cold air coming in from a much higher latitude.
“We expect these conditions to remain in place until at least next weekend and possibly longer, because sometimes these conditions can be quite stubborn and not easily subject to change.”
The Met Office said travel disruption was likely and journey times by car, train and bus could take longer than usual.
People are at risk of slipping and falling on icy patches of untreated roads, pavements and paths while some rural communities could become cut off from the power grid.
Dale Hipkiss, the national network manager at National Highways, said people should keep warm clothes and a torch in their car in case they got stuck in icy conditions.
He said: “Freezing conditions bring so many hazards such as snow and ice. Take every possible step to understand your journey in advance and allow lots of extra time when travelling to prepare for the unexpected.”
The UK Health Security Agency has issued a level 3 cold weather alert for the whole of England, which is likely to be reviewed in the coming days.
The agency’s head of extreme events and health protection, Dr Agostinho Moreira de Sousa, said people should check on vulnerable relatives and advised pensioners and anyone with an underlying health condition to heat their home to at least 18C.