Heavy snow and strong winds leading to blizzard conditions in some places. A red warning has been issued for south Wales. Nick Miller has all the details.
Much of the UK is braced for snow as the cold weather threatens to cause severe disruption.
A red Met Office warning for snow was issued for parts of Wales on Friday.
BBC Weather predicted snow after midnight in Wales and south-west England, spreading across central and southern England. Northern Ireland and eastern Scotland will also be affected.
Up to 25cm of snow is expected on high ground with overnight temperatures expected to fall as low as -5C (23F).
Blizzards and strong winds are set to make driving conditions difficult on the roads, and motorists are being warned that heavy snow in much of the UK will arrive before the morning rush-hour.
Predictions and warnings have been made regarding much of the country:
- The Met Office's red warning for snow, which is rare and means all non-essential travel should be avoided as severe disruption is very likely, applies to the southeastern side of the Brecon Beacons and Black Mountains
- Amber severe weather warnings, which mean be prepared for disruption and only travel if necessary, are in place across large parts of central, western and southern England and Wales, as well as Northern Ireland. Snow is expected in northern England later on Friday
- BBC weather said Northern Ireland would experience rain early on Friday, which would turn to snow during the course of the day, with between 10cm and 15cm expected in most areas and about 20cm over hills
- Travellers across England are warned of road and rail disruption ahead of "significant snow" and some trains will be cancelled or revised in south and south-west England as operators prepare for Friday's heavy snowfall
- London is braced for disruption, while authorities in Berkshire, Oxfordshire,Bristol,Somerset and Kent are among those who have begun preparations for snow
- Schools in many parts of the UK may close on Friday
- Cold weather payments are set to surge as a result of the freezing weather. The Department for Work and Pensions says icy conditions have already triggered cold weather payments to two million people, totalling £50m, over the last week alone.
BBC weather forecaster Mike Silverstone said much of England and Wales would experience between 5cm and 15cm of snow on Friday, whereas Northern Ireland could see up to 20cm by Saturday morning.
Continue reading the main storyHe said: "People should take a great deal of care because it's going to be treacherous out there."
Forecasts suggest daytime temperatures are likely to remain below freezing in many areas, with the wind chill factor making it feel even colder.
The snow was expected to ease off later on Friday, although it is set to remain in eastern areas.
Forecasters say it is likely to stay very cold over the weekend.
BBC Weather said snow was likely to be confined to Scotland, north-eastern England and Northern Ireland on Saturday.
Much of eastern England has been under a blanket of snow for several days
However, low temperatures may mean much of the snow that falls elsewhere on Friday will not thaw.
The Highways Agency has put road ploughs and snow blowers on stand-by to clear major routes.
Steve Crosthwaite, who heads the agency's National Traffic Operations Centre, urged drivers to allow more time for morning travel.
He added: "During periods of severe weather we also suggest people consider whether their journey is essential."
For more information on the weather and transport situation in your area, visit the BBC Weather website and BBC Travel News.
Are you in Wales? How are you preparing for the snow?