Commuters are being warned to prepare for major disruption this morning after heavy snowfall blanketed huge swathes of the UK overnight.
Forecasters said more than 20cm of snow could settle by Wednesday with the country potentially facing its coldest weather since 1991.
Temperatures in the capital are not expected to rise any higher than zero degrees on Tuesday, with the Met Office warning it will feel “bitterly cold”.
Delays and cancellations are expected on the rail network and at airports, while pavements and cycle lanes could be very icy.
Forecaster Marco Petagna said there would be some “quite treacherous driving conditions” as many make their way into work.
“Most people will have to travel, but if you don’t have to travel – it is best to try to avoid if you can within those amber warnings,” he said.
Schools could also be hit by closures due to the heavy snowfall, as school leaders said keeping staff and pupils safe should be a top priority.
Paul Whiteman, the general secretary of the National Association of Head Teachers (NAHT), said: “Schools should stay open if they possibly can but safety concerns are the most important.
“If it’s not safe for the school to be open then it is fine to close.
“You have to take into consideration journeys at the beginning and the end of the day, as conditions may change whilst the school is open. It is important that staff and parents can get home at the end of the day as well.”
Conditions are not likely to improve for several days, with forecasters warning that snow will continue will into the week.
More snow showers are forecast throughout the week in London, with more travel disruption likely amid extremely low temperatures.
An amber snow warning is in place for the north east of England and Scotland from 6am on Wednesday to 12pm on Thursday, with up to 40cm of snow expected to fall during that period.
Mr Petagna said daytime temperatures would “struggle to get above freezing” across many areas.
“Add on the effect of that wind, and the wind is going to pick up come Wednesday, so it is going to start to feel even colder still,” he added.
Forecaster Frank Saunders said parts of the country could see their “coldest spell of weather since at least 2013, and possibly since 1991”.
It is expected that the mercury could plummet to minus 15C by midweek where there is snow on the ground, rivalling temperatures forecast for parts of northern Norway and Iceland.
Many local authorities said they were ready to react to the adverse conditions, with Kent County Council even stating all resources would be focused on keeping highways clear.
On Monday, British Airways cancelled more than 60 short haul flights either departing or arriving from London Heathrow in a bid to protect punctuality.
And ahead of Tuesday’s snowfall, many airports were advising passengers to check with their airlines before travelling.
Greater Anglia also ended services early to enable trains to return to depots and stations early on Monday, as the provider said limited timetables would be in place on Tuesday – with 200 trains cancelled.
Network Rail revealed it would also be putting heaters and Nasa-grade insulation on to points on the tracks in a bid to prevent ice forming overnight.
The NHS could also struggle to cope with the extra strain caused by the wintry weather, doctors have warned, and people have been encouraged to check on elderly or vulnerable neighbours.
The public have also been asked to look out for the homeless and report anyone sleeping rough in the freezing conditions to their local council.
From Thursday, forecasters predict that another weather system, Storm Emma, will bring blizzards, gales and sleet as it meets the chilly Beast from the East later this week.
The storm, named by the Portuguese Met Service, will move north through Europe and is due to hit the UK on Thursday and Friday, and will be “significantly disruptive”, bringing the risk of power cuts and transport delays.