Ice and snow warnings issued as temperatures plummet
There could be severe travel disruption on the roads, trains and even at airports
Large areas of the country have been warned to expect severe conditions during the weekend, with snow forecast for Scotland.
Temperatures are set to stay low, hitting minus 10C (14F) in isolated areas on Saturday and Sunday.
A Met Office yellow warning for snow and ice is in place for much of Scotland until 12pm on Sunday.
On Saturday, the Met Office extended ice warnings in Northern Ireland, Wales and south-western England to cover snow until 12pm on Sunday.
On Sunday, a snow and ice warning kicks in at 9am for most of London and some of south-eastern England until 9am on Monday, with a 30% chance of up to 5cm of snow.
The Met Office said the conditions could lead to travel disruption, especially on Monday morning, and a small chance of some rural communities becoming cut off along with a possibility of power cuts and mobile phone coverage being affected.
Met Office chief meteorologist Steve Willington said: "It is staying cold with daytime temperatures remaining only a few degrees above freezing in many places over the coming days and overnight temperatures dropping to minus 10C or lower in isolated spots.
"Although below average, these temperatures are not that unusual for this time of year.
The UKHSA is advising people to look out for friends and family who are vulnerable in the cold and to ensure they have access to warm food and drinks, adding that people should maintain indoor temperatures of at least 18C (64.4F).
Dr Agostinho Sousa, consultant in public health medicine at UKHSA, said: "Cold weather can have serious consequences for health and older people and those with heart or lung conditions can be particularly at risk.
"If you have a pre-existing medical condition, you should heat your home to a temperature that is comfortable for you.
"In rooms you mostly use such as the living room or bedroom, try to heat them to at least 18C if you can. Keep your bedroom windows closed at night. Wearing several layers of clothing will keep you warmer than one thicker layer."