The "Beast from the East" has hit the UK,with temperatures plummeting and snow falling across the country. Conditions are due to worsen as the week progresses, and transport has already been affected.
Train companies have put out advice about when to travel and whether to expect delays as the Met Office gives out amber and yellow snow warnings.
Here is the latest travel information.
The South East is set to be hit with snow next week with 'The Beast from the East' or ‘polar vortex’ causing one of the UK’s coldest weeks in recent years.— NR South East (@NetworkRailSE) February 23, 2018
Here's what we're doing to try & keep trains running for @Se_Railway@SouthernRailUK@TLRailUK &@GatwickExpress passengers pic.twitter.com/H1wqPIMnnI
Network Rail has put special measures in place to prevent electric tracks from freezing over, so the trains can continue to run.
However, rail companies across the country have warned that there will be delays and cancellations from Monday morning as heavy snowfall is predicted.
It is getting colder this week, with snow expected later today. We're working closely with @NetworkRailSE to keep the network open, but please check before you travel. #UKSnowpic.twitter.com/nb9NuuNmoL— Southeastern (@Se_Railway) February 26, 2018
Commuters have been warned to allow extra time for their journeys and to check the train schedules before they set off.
Greater Anglia and Southeastern services have advised commuters try to travel before 6pm on Monday evening to avoid disruption.
There were severe delays on the Tube at rush hour, which could continue throughout the day.
TfL advised: "Please wrap up warm and check your journeys before you travel, allowing extra time for your journeys where necessary."
For more information on services on Monday evening please see the attached poster: pic.twitter.com/73Df83cy0t— TfL Rail (@TfLRail) February 26, 2018
TfL Rail has suspended all services from 11pm tonight due to the snow and on Tuesday trains will not start until 7am and it will be a limited service of six trains per hour between London Liverpool Street and Shenfield.
The operator warned there may be unexpected and sudden cancellations due to the cold weather.
While the morning commute was fine for many as snow began to fall, there are expected to be delays on some parts of the motorway this evening.
Highways England said: "Feeling bitterly cold in easterly winds, gusting 30 mph in eastern parts and around showers, this enough to cause drifting where any snow lies on areas surrounding routes.
"Later in the evening there will be some respite as the showers ease for a time, although snow showers will continue in Norfolk, Suffolk and Lincolnshire.
"The A12 Essex and M2/M20 Kent and eastern parts of the M25 becomes exposed to lines of showers, bringing some very difficult driving conditions and significant disruption.
"During the early morning, a band of snow moves into the Northeast, bringing a risk of disruption due to the heavy snowfall. Towards the morning rush; this snowfall reaching southern parts of the Northwest, and northern parts of the Midlands."
British Airways has cancelled a number of flights as of Monday morning as the weather worsens.
The airline has cancelled at least 36 flights from Heathrow Airport today, and apologised to customers.
A statement on the British Airways websites states: “We are sorry that the weather is likely to lead to some delays and disruption to our schedules.
“We have proactively cancelled some services and will be re-booking customers on to alternative flights or offering them a full refund if they no longer wish to travel.
“We are sorry for the disruption to your travel plans and are doing all we can to minimise the effect the poor weather is having on flights.”
Flights affected include those to the UK and Europe as well as New York and Los Angeles.
BA said passengers with cancelled flights should not travel to the airport.