A 12-hour warning has been issued by the Met Office with snow and ice expected to continue overnight while temperatures plunge to as low as -9C.
A yellow weather warning remains in place across Cornwall, South Wales, parts of the Midlands, London and East Anglia until 3am on Tuesday.
The forecaster warns of "ice and small amounts of snow" which could lead to "slippery surfaces and icy patches."
Tuesday night is expected to see temperatures drop to -9C in the Scottish Highlands while daytime temperatures are likely to top 6C in the south and 8C in the north.
The forecaster warns of 'ice and small amounts of snow' which could lead to 'slippery surfaces and icy patches'
Met Office
The cold snap is set to stay this week as Britons brace for "wintry showers" and very cold conditions.
A Met Office forecaster said: "A mix of sleet and snow showers will move in from the east later on Sunday night along with temperatures near zero.
"Given these wintry showers, and also wet surfaces after recent wet weather, some icy patches are likely on untreated surfaces.
"Additionally a few of the snow showers could turn quite heavy; these probably only affecting a narrow zone but a few places could see 1 to 3cm, mainly over the north Downs and on grassy surfaces."
LATEST DEVELOPMENTS:
A person walking through a snow flurry in Lenham, Kent as heavy snow hits Britain
PA
The UKHSA and the Met Office have also issued an amber Cold-Health Alert (CHA) for the North West of England, West Midlands, East Midlands and South West of England until 12pm on Friday.
Dr Agostinho Sousa, Head of Extreme Events and Health Protection at UKHSA, said: "With the Met Office forecasting drops in temperature across the United Kingdom into next week, it is important to check in on the wellbeing of those most vulnerable to the cold.
"Cold weather can increase the risks of heart attacks, strokes, and chest infections, so it can have a serious impact on health, particularly for older people and those with pre-existing health conditions.
"Temperatures are expected to turn particularly cold overnight, as we would expect at this time of year. If you have a pre-existing medical condition or are over the age of 65 it is important to try and heat the rooms where you spend most of your time, such as your living room or bedroom, in the coming days."
The cold snap is set to stay this week as Britons brace for 'wintry showers' and very cold conditions
Netweather
The UKHSA and the Met Office have also issued an amber Cold-Health Alert (CHA) for the North West of England, West Midlands, East Midlands and South West of England until 12pm on Friday
PA
Weather experts at NetWeather have warned cool air is blustering towards Britain via the Baltic Sea.
Met Office spokesperson Stephen Dixon added added that clear conditions and some sunny spells are expected.
He went on: "It is a cold regime and that theme continues for much of the week
"Temperatures through the week will remain below average for this time of year. If you do have to travel in icy conditions plan your route, check for delays and road closures.
"If you are driving … look out for potential hazards and keep your speed down. Using a higher gear may be more appropriate."
