Health workers were put on alert by the Government last night as Britain braced itself for snow.
The Level Two weather warning puts them under orders to make daily visits or phone calls to the old, ill and vulnerable.
Hospitals and doctors surgeries will also be on alert for 'a potential influx of weather-related injuries and illnesses'.
The weather warning comes into force from 6am tomorrow as average daytime temperatures are expected to plunge to around 2C.
Experts warn the freeze from Russia could last up to three weeks, with snow predicted for much of the country by next week.
Met Office chief forecaster Paul Gundersen said: "All parts of the UK will see cold weather setting in over the weekend.
"We can expect sleet and snow showers to affect eastern areas at times, but with a battle developing between the cold air in the east and mild air pushing in from the west, no one should be surprised to see sleet or snow over the weekend and next week."
Forecaster Brian Gaze of The Weather Outlook added the UK should prepare itself for "ice box conditions."
Snowploughs were last night being readied as hundreds of gritting lorries dug into a three million-tonne salt stockpile.
Council staff are on standby to clear snow near schools and shops.
The Local Government Association's Peter Box said: "People can count on councils to keep roads safe."
Scotland's Transport Minister Keith Brown added: "I'm confident we'll keep Scotland moving."
However, many Brits are totally unprepared for difficult winter driving conditions.
Online insurer quotemehappy.com found almost half the motorists they quizzed admitted they couldn't change a tyre with 16% saying they had no idea how to open their bonnet.
More than a fifth didn't have the foggiest about how to use their fog lights, less than half carry a first aid kit and more than 40% don't carry out their breakdown cover contact details in their car.
And the Environment Agency last night still had 49 flood warnings and alerts in place after the recent deluge of wet weather with teams out in Kent monitoring rising groundwater levels.
Level Two weather warnings are put out when the Met Office are 60% sure of the incoming weather-front.
When it actually hits, the country will move up to Level Three - one stage behind a full-scale emergency situation.
How to survive the cold snap heading our way
An extra 8,000 people die for every one degree drop in average temperature - even in mild winters.
Being cold makes blood pressure go up, raising the risk of heart attack and stroke. And it increases the risk and severity of flu, chest infections and other respiratory problems.
Age UK's advice for older people this winter is:
1 Keep your living room at 21C (70F). It's harder to judge temperatures as you get older, so use a thermometer to ensure you detect changes and act quickly.
2. Close your windows at night and keep your bedroom at 18C. Sleeping with the window open all year round is NOT healthy. On a winter night it will put you at greater risk of a heart attack or a stroke.
3 Wrap up well and protect your fingers, mouth and head from cold. Breathing in cold air can increase your chances of becoming ill.
4 Stay flu-free. Get a jab - free to over-65s - keep warm and eat well to help ward off infection.
So strat's what it is! Sudden stratospheric warming
The extreme cold forecast next week is linked to upper atmosphere changes in a process called sudden stratospheric warming.
Often heralding the onset of a big freeze, the mechanism involves rapid warming in just a couple of days about six to 30 miles up.
Colder easterly winds are brought in and they slow down or even reverse our usual milder westerlies.
The jet stream moves south and cold air from the east is dragged in.