Temperatures will plunge below freezing across large swathes of the UK tonight as the Met Office warns that severe cold weather and icy conditions could increase health risks to vulnerable patients and disrupt services.
Many regions will struggle to rise above zero overnight, while some areas of high ground could see as much as 4in-6in (10cm-15cm) of snow, and yellow warnings of snow and ice have been issued for much of the UK.
England is likely to experience colder than average conditions over the next five days, but a spokeswoman for the Met Office said that overall it is a case of "typical British winter weather".
Parts of England, in areas above 656ft (200m), could see 0.8in-1.6in (2cm-4cm) of snow between 3am and noon tomorrow, with places expected to be hit including Devon, the Chiltern Hills, the Cotswolds, as well as mountains and high hills in Wales.
Met Office spokeswoman Laura Young said other places, such as Cumbria and the Lake District, could see 4in-6in (10cm-15cm) of snow in areas above 984ft (300m).
She added: "It doesn't really warm up in Scotland and northern parts of England all weekend, so there is a very good potential for ice on Sunday. People really need to be aware of that.
"Basically, snow and sleet, then it becomes very, very clear, but then the temperatures really drop, and then it freezes."
Ms Young said that, despite the number of warnings, there has not been a record number.
She said that by this time last year, almost every day had had some form of severe weather warning since the beginning of December - mostly wind and rain - while there have been fewer this winter.
"We have very short memories, as human beings, for weather. We're forgetting that this time last year huge parts of the country were completely under water.
"We also just had all the storms over Christmas (2013) ... some people were still without power by now," she said, also pointing out the storms that battered Britain in February.
Ms Young said that while it is "colder than average", and there are more snow and ice warnings than this time last year, the current weather is "typical British winter weather".
While it may be "typical", the Met Office has issued an amber severe cold weather alert for north east and north west England, Yorkshire and Humber, and the East and West Midlands.
The amber alert, level three, "requires social and healthcare services to target specific actions at high-risk groups", the Met Office website said.
South west England, south east England and the east of England have been issued with a yellow alert for "alert and readiness".
Regarding the amber alert, the Met Office website said: "There is a 90% probability of severe cold weather/icy conditions between 0800 on Friday and 1200 on Tuesday in parts of England.
"This weather could increase the health risks to vulnerable patients and disrupt the delivery of services. Please refer to the national Cold Weather Plan and your Trust's emergency plan for appropriate preventive action.
"England is likely to experience colder-than-average conditions in the coming five-day period, with widespread overnight frosts. Some wintry precipitation can be expected for most areas too, mostly in the form of scattered showers, leading to lying snow and icy stretches in places.
"There is currently a good deal of uncertainty about the expected weather over south east England on Sunday, with a period of persistent rain potentially turning to sleet or snow over hills. Please stay in touch with the weather forecast for latest developments."
Most parts of Scotland tonight will struggle to get above 0C (32F), with the mercury in Inverness expected to drop to minus 2C (28.4F), Ms Young said.
The average temperature in Northern Ireland is expected to be 0C (32F), with some places in the west possibly seeing a slightly warmer 1C (33.8F).
Central England is not going to get above freezing, and will most likely be as low as minus 1C (30.2F) or minus 2C (28.4F), while southern England could also see those low temperatures, and Kew Gardens in London is expected to be minus 3C (26.6F).
Meanwhile, Wales will be 0C (32F) in some parts, but other areas such as Aberystwyth will be 2C (35.6F) as it benefits from some shelter from Northern Ireland, and Holyhead is expected to be as high as 4C (39.2F).
Public Health England (PHE) have urged people to help vulnerable family and friends to keep warm.
Dr Angie Bone, of PHE's extreme events team, said: " Cold does kill, even in places where the temperatures aren't at their lowest. Most of our advice on keeping warm in cold weather may seem like common sense, but it's important that we make the point that people should think about how cold can affect them.
"Our advice is that when indoors, have plenty of warm food and drinks to stay warm and try to maintain indoor temperatures to at least 18C (64.4F), particularly if you are not mobile, have long-term illness or are 65 or over.
"This is also a good time to think about how the bad weather may affect your friends and family, particularly if they are older or very young or have pre-existing health conditions. These groups can be particularly vulnerable to the ill-effects of cold so think now what you could do to help."
Yesterday, one man was killed when a tree fell on his car in Co Antrim, while 5ft (1.5m) of snow in parts of Scotland left motorists stranded overnight on the A9 route to the Highlands.
Earlier, high winds and heavy rain caused delays in parts of Scotland and on the south coast of England.
Several trains between Glasgow and Ayr were cancelled and replaced by buses, while Southern, South West Trains and First Great Western services between Portsmouth Harbour and Havant were delayed by up to 30 minutes due to an emergency incident near Hilsea, according to National Rail.
Age UK's charity director, Caroline Abrahams, urged older people to "take basic precautions" during the cold spell, and called on the Government to "commit to improving the energy efficiency of homes across the country" in a bid to end preventable winter deaths.
"The cold weather can be particularly dangerous for older people who are more at risk of suffering health problems when the temperature drops," she said.
"During this cold spell we are urging all older people to keep warm and take basic precautions to protect their health - for example, sleeping with the windows closed at night to lower the risk of heart attacks and strokes caused by raised blood pressure brought on by the cold.
"It's a shocking fact that this winter one older person could die every seven minutes from the cold. Yet, with just under one million older people living in fuel poverty, many simply cannot afford to heat their homes to a temperature high enough to keep warm and well."
She added: "We are calling for the Government to commit to improving the energy efficiency of homes across the country in order to provide a long-lasting solution to the scandal of fuel poverty and preventable winter deaths."