People are being urged to check on the elderly and vulnerable as more heavy snow and icy conditions are forecast to hit the UK.
The Met Office issued amber weather warnings for snow in the east and southeast of England for Sunday, stretching from Norwich down to Canterbury, and warned that hazardous conditions could last well into next week.
It also extended its yellow warnings for snow and ice, covering the entire length of the UK, from midday on Saturday to midday on Wednesday.
The Met Office's chief meteorologist, Paul Gundersen, said: "The UK is in for a notably cold and snowy period over the next week, with very cold air in place over the whole of the UK by Sunday.
"Showers will see snow accumulating across eastern areas. Within the amber warning area, more widespread snow is expected and we could see 5-10cm of snow quite widely, with a chance that a few places could see 20cm or more."
Temperatures will likely go below freezing for many on Sunday, and by Monday the average daytime temperature will only be between 1C and 4C across the country.
It's a stark drop from the comparatively mild temperatures of Friday, with the mercury having climbed to 11C in some places earlier, and a possible return to the Christmassy conditions experienced by many last month.
The RAC has warned it is bracing itself for a sharp increase in breakdowns in the coming days, and said that people should think "extremely carefully" before setting out on journeys.
People are only meant to leave their home for a very limited number of reasons anyway, due to lockdown rules.
With widespread overnight frosts and wind chill making daytime temperatures feel freezing, Public Health England is advising people to check in with elderly and vulnerable relatives and neighbours.
Dr Owen Landeg, group leader of extreme events and health protection, said that for older people and for those with heart and lung problems, the cold can "increase the risks of heart attacks, strokes and chest infections".
He added: "It's really crucial at this time, especially ahead of a very cold snap, to remember to check on frail or older neighbours or relatives, especially those living alone or who have serious illnesses."
People are being advised to call those who may be in need of help and support, or to make a "socially-distanced doorstep visit" to check they have enough food, drinks and any medicines they need.
The government and the NHS will also be hoping that the potentially disruptive weather doesn't impact the UK's increasingly impressive coronavirus vaccine rollout.
Simon Partridge, a Met Office meteorologist, has said that continuous snow showers and strong wind in the East on Sunday would result in "really bad" visibility and up to 20cm of snow in some areas.
Mr Partridge warned: "As the snow is blowing around, obviously there may be places where it will accumulate more because it will drift.
"That means significant disruption - and obviously at the moment with vaccination centres open seven days a week, that can have a knock-on effect there as well."
Kent was left relatively unscathed by last month's snowfall, but people there have been warned to expect some more this time round.
Kent County Council's deputy director for public health, Allison Duggal, said: "It is vital that during this prolonged period of severe weather, people act to keep themselves and their home warm - even if this is just by heating the bedroom and living room."
It comes after drivers were left stranded in two-metre snow drifts in northern Scotland on Friday, and amber warnings remain in place there until midday on Saturday.
Ben Aldous, from the RAC, said: "As patrols, we are well equipped to deal with the severe cold, but we urge drivers to think extremely carefully before setting out and question whether their journey is absolutely necessary.
"For anyone who has to drive, we'd strongly advise making sure their vehicle is ready for the cold."