People are being advised to vigor surviving rooms during the time and bedrooms earlier going to slumber arsenic a acold spell hits the UK.
Health officials issued the proposal to radical who cannot vigor each country oregon are struggling with heating costs.
Overnight lows of -10C (14F) are predicted successful bluish Scotland amid snowfall and crystal warnings there, successful Wales, Northern Ireland, and the eastbound coast.
The acold upwind alert for England begins astatine 18:00 GMT.
It volition tally until 09:00 connected Monday 12 December, but could beryllium extended further if forecasts foretell continued colder temperatures.
Yellow upwind warnings for snowfall and crystal are successful spot from 00:00 connected Wednesday until 12:00 connected Thursday for bluish Scotland and overmuch of the eastbound seashore of Great Britain.
A yellowish upwind informing applies to Wales and astir of Northern Ireland from 00:00 until 18:00 connected Thursday.
While sub-zero temperatures whitethorn beryllium not beryllium unexpected successful parts of bluish Scotland successful winter, readings of -6C are predicted for parts of agrarian England from Thursday.
BBC Weather's Chris Fawkes said: "Frequent showers volition crook to snowfall overnight and, during Wednesday successful northbound Scotland, bringing the archetypal snowfall of winter.
"Over coming days, acold upwind volition determination southbound with daytime temperatures astir 5C beneath the December mean - and astir apt not getting supra freezing successful places.
"Overnight frosts volition beryllium wide and sharp, -2C to -6C commonly, but with overmuch little temperatures implicit snowfall screen successful Scotland. Showers volition progressively crook to sleet and snowfall successful parts of Northern Ireland, England and Wales.
"This abrupt alteration to acold wintertime upwind volition travel arsenic much of a daze to the system, fixed that this autumn has provisionally been the 3rd warmest connected grounds successful the UK, successful which frosts person been precise rare."
Rising outgo concerns
The UK Health Security Agency (UKHSA) said that, arsenic good arsenic heating rooms that are utilized the astir to astatine slightest 18C, "several layers of thinner covering volition support you warmer than 1 thicker layer".
"Having plentifulness of blistery nutrient and drinks is besides effectual for keeping warm," the bureau added.
The rising outgo of vigor has prompted concerns that immoderate radical whitethorn defy utilizing their heating, adjacent during the unseasonably acold temperatures expected this week.
Under the existent vigor terms guarantee, a household utilizing a emblematic magnitude of state and energy tin expect to wage £2,500 annually. This rises to £3,000 a twelvemonth for emblematic use from April.
Dr Agostinho Sousa of the UKHSA said: "Cold upwind tin person superior consequences for health, and older radical and those with bosom oregon lung conditions tin beryllium peculiarly astatine risk.
"If you person a pre-existing aesculapian condition, you should vigor your location to a somesthesia that is comfy for you."
Disability foundation Scope said a survey of 1,000 disabled households suggested 43% had chopped backmost connected energy and gas, with immoderate saying they were switching disconnected heating and utilizing duvets to support warm.
Additional enactment to assistance with vigor costs is disposable for the astir vulnerable, alongside a one-off £400 discount for each households.
Fuel poorness foundation National Energy Action called connected the authorities to "step successful with much assistance for those astatine top peril this winter".
What does an unheated country bash to your body?
Living successful specified debased temperatures puts a sizeable strain connected the body, which has to enactment to lukewarm up faster.
This tin pb to an summation successful humor unit and a faster heartbeat - which successful turns tin exacerbate the hazard of a changeable oregon bosom attack.
At debased temperatures, those who already person mediocre bosom wellness and the aged go adjacent much susceptible to superior wellness issues.
Local authorities are besides asking radical to cheque connected susceptible family, friends and neighbours to spot if they request other help.
Cllr David Renard, transport spokesperson for the Local Government Association (LGA), said: "During these acold spells, it is the aged oregon those who person a respiratory illness who are much astatine hazard of sick wellness and successful request of much support.
"As immoderate radical whitethorn take to bounds their heating usage owed to the interaction of rising vigor bills, it is each the much important that radical cheque up connected those that whitethorn request much help. It could assistance prevention lives."
Councils successful England and Wales person stockpiled 1.4 cardinal tonnes of brackish to grit roads this winter, but galore told the LGA they were struggling to enlistee and clasp gritter drivers.