Commuters are being warned of travel chaos from ice and snow across Britain today, with three weather warnings having been issued by the Met Office.
Overnight temperatures plummeted to some of the lowest so far this winter, while a fresh onslaught of snow and ice means roads could be treacherous.
Forecasters are predicting 15cm of snow to fall quickly, with potential for up to 5cm at sea level, with the Highlands expected to face of the brunt of wintry showers.
Yellow weather warnings are in place throughout much of Scotland, as well as northern Ireland, until 11am, and a large portion of the west coast of England could be frozen over until 10am.
The icy blast will batter large swathes of the country, from Carmarthenshire in Wales to North Yorkshire.
A loss of power supply is likely in some areas.
This means roads and railways could be severely impacted with longer journey times and delays to bus and train services expected - while gritters will be battling against the elements.
Those traveling in heavy snow and ice are advised not to be tempted to overtake gritter trucks and to slow down, as it can take 10 times longer to stop in snowy or icy conditions, and stay in the lowest gear possible.
A Met Office forecaster said: "An area of sleet and snow is likely to move eastwards overnight, followed by a few wintry showers.
"Surfaces will then be freezing, leading to icy stretches. There is a small chance that up to 5 cm of snow could fall down to sea level. Snow over high ground is much more likely, with 5-10 cm above 250 m and as much as 15 cm above 350 m."
The forecaster added: "Frequent showers will affect the northwest of Scotland overnight Sunday and through Monday. Falling snow will reach low levels away from the western coastal fringes by dawn.
"Some spots may see accumulations of 1-3 cm below 150 m, with more widely 5-10 cm above 150 m and 15 cm above 300 m.
"Strong winds may also bring temporary blizzard conditions in association with the showers. Also icy patches becoming widespread away from western coasts, bringing some travel disruption."
Forecasters have also reminded people to take care walking as there is a chance of injuries from slips and falls on icy surfaces.
Simon Partridge, of the Met Office, said while it is unclear if Monday night will prove to have been the coldest so far, "we'll certainly have two cold days".
Meanwhile, conditions will continue to be unsettled later on in the week with spells of rain and strong winds, and possible gales.
The Met Office's long range forecast is warning of "often windy" conditions with outbreaks of rain for all areas over the weekend, though temperatures will be "on the mild side of the seasonal average".
As we head through the first full week of February it currently looks most likely that we will see a gradual trend towards more settled conditions," the report added.
UK 5 day weather forecast
Today:
Icy stretches expected for the north this morning with wintry showers continuing for western and northern areas, mainly for high ground. Eastern parts of the country will stay mostly dry, away from the far northeast. Windy and cold.
Tonight:
Showers continuing for western and northern parts though these easing from the southwest overnight and wintriness increasingly for high ground in the northwest. Staying cold and windy.
Wednesday:
Showers at first in the far north but mostly dry elsewhere. Becoming cloudier from the west with some rain developing for western areas, particularly western Scotland. Less cold than Tuesday.
Outlook for Thursday to Saturday:
Remaining unsettled, with spells of wind and rain at times, heaviest for northwestern areas. Often drier across southeastern areas. Mild generally, locally very mild on Friday.
