A blast of wintry snow dubbed "the Beast from the East" has hit Britain, bringing warnings of chaos on the roads and in hospitals.
The wintry blast swept into the UK on Monday morning, and means that some parts of the country are set to feel colder than the Arctic Circle as freezing temperatures continue into the week ahead.
Train services are expected to be cancelled or delayed as the snow sets in, and doctors have warned that the NHS could struggle to cope with the extra strain caused by the weather.
People are being warned to check on elderly or vulnerable neighbours during the cold spell.
The public has also been asked to look out for the homeless and report anyone sleeping rough in the freezing conditions to their local council.
Amber warnings of snow have been issued by the Met Office for north-east, central and south-eastern England on Tuesday, and eastern Scotland on Wednesday.
It warned that some rural communities could become cut off, with power outages and disruption to mobile phone services likely.
By the middle of the week, the majority of Britain is being warned of the potential for delays on the roads, trains and in the air.
A less severe yellow warning for snow is in place from Monday to Wednesday.
Greater Anglia (GA) said it was limiting its services from Monday in anticipation of the snowy blast.
South Eastern urged passengers to finish their journeys before 6pm on Monday to avoid potential disruption.
Transport for London (TfL) warned passengers to check ahead of their journeys as disruptions were possible on Underground and Overground services due to the low temperatures forecast.
Train operator C2C also warned of limited services, advising trips after 9pm on Monday could be altered or cancelled.
Lows of minus 5C (23F) recorded over the weekend marked the lowest temperature in the week leading up to March 1, the first day of spring, since 1986.
The wind chill, which could see parts of the UK feeling as cold as minus 15C (5F), rivals the temperatures forecast for parts of northern Norway and Iceland.
The Met Office said that by the end of Wednesday, more than 20cm of snow may have accumulated in some parts of eastern England, Scotland and Northern Ireland.