The early signs of spring that have been in evidence after a mild December look set to be blasted away over the weekend as temperatures plummet across the country.
The Met Office has warned that severe cold weather in parts of the country could increase the health risks for the very young, very old and vulnerable patients.
The weather could also disrupt the delivery of services, it said.
Sky News meterologist Chris England said: "After a period of southerly winds, which have kept it very mild, a northerly flow has brought some fairly clear, cold Arctic air across Britain and Ireland.
"With a high pressure system developing over Britain, that cold air is going to hang around for a while, bringing sunshine by day and a widespread frost by night. There will be some mist and fog as well, some of it dense and freezing.
"The cold snap will be a shock to the system, but it is worth remembering that temperatures will only be around average for the time of year - the recent warmth is the oddity."
The cold weather is expected to hang around until at least Monday, with the North West, North East and Yorkshire & Humber regions of England expected to be hardest hit.
Daffodils and crocuses have already bloomed in some parts of the country due to
the mild winter but the cold snap could nip that in the bud.
Wildlife experts also said that the sudden cold weather could bring a sudden influx of wintering birds to the UK's reserves.
Slimbridge Wetland Centre in Gloucestershire said the mild winter had so far kept some birds further north, but the change in the weather may lead to a delayed migration.
Dave Paynter, reserve manager, said: "This year we have seen higher numbers of waders enjoying the warm wet weather such as flocks of lapwing, dunlin and golden plover, but have so far failed to see the numbers of geese, ducks and swans we would expect.
"This is because the weather has been so mild that they have stopped early on their migration as it is easier for them to find food further north."
Last winter was the coldest for 31 years in the UK with an average December to February temperature of 1.51C and new research suggests that warmer Arctic summers may be bringing repeated colder winters.
High pressure in the northern polar regions is thought to push colder air into mid-latitude regions, producing chillier winters.
Cold snaps can occur for a multitude of reasons to do with natural climate variability, but the scientists from the US-based climate consultants Atmospheric and Environmental Research Inc believe they can see a trend linked to increased autumn snow over northern Europe and Asia.
According to the theory, warmer conditions combined with melting sea ice allow the Arctic atmosphere to hold more moisture.
This in turn increases the likelihood of precipitation - most probably snow - across more southerly regions.
The increased snow cover has an impact on the Arctic Oscillation, a pressure pattern that affects climate in mid-to-high latitudes.