A cold weather alert has been issued for all of England as much of the country braces for snow and icy conditions.
The Met Office has already issued a yellow warning for snow and ice which is set to come into force tonight for Midlands, much of Wales and the southeast, including London.
Warnings are also in place across northeast England, Northern Ireland and Scotland, with up to 30cm of snow expected to fall in isolated spots across Scotland.
The UK Health Security Agency’s (UKHSA) level three cold weather alert warns of a 90% probability of severe cold weather, icy conditions and heavy snow between 9am on Monday 6 March and 11.59pm on Thursday 9 March in parts of England.
The alert urges people to “look out for friends and family who may be vulnerable to the cold, and ensure they have access to warm food and drinks and are managing to heat their homes adequately”.
Patchy snow of 1-2cm could accumulate over much of Wales and parts of central, southern and eastern England, with temperatures dropping as low as -1C (30F) in Manchester, and 2C (35F) in London, on Monday night.
The Met Office’s warning is in place from 9pm on Monday until 10am on Tuesday.
Read the Sky News weather forecast
It comes as Arctic air moves over Scotland and down towards northern England.
The Met Office said frequent snow showers are expected in northern Scotland from Monday afternoon, with temperatures potentially dropping below -10C (14F) during the night.
The wintry conditions could lead to up to 10cm of snow on higher ground in Scotland and 5cm at lower levels.
The Met Office advises the weather could cause disruption to travel, with “some roads and railways likely to be affected with longer journey times by road, bus and train services”.
It brought the warnings forward to Sunday evening having earlier announced them for Monday and Tuesday.
Met Office spokesman Grahame Madge said: “Temperatures will be much, much colder than we would expect at this time of year.
“The pattern will set in for some time. We have got this feed of cold air coming in from a much higher latitude.
“We expect these conditions to remain in place until at least next weekend and possibly longer because sometimes these conditions can be quite stubborn and not easily subject to change.
“This is a disruptive spell of weather which could have quite serious consequences for some.”
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Areas affected by the warnings could experience power outages, delays to road, rail and air travel and icy surfaces, and some rural communities may be cut off by the freezing conditions.
Dr Agostinho Sousa, head of extreme events and health protection at UKHSA, said: “During periods like this, it is important to check in on family, friends and relatives who may be more vulnerable to the cold weather, as it can have a serious impact on health.
“If you have a pre-existing medical condition or are over the age of 65, it is important to try and heat your home to at least 18C if you can.”