Heavy snow is sweeping eastwards across the UK, disrupting travel and leaving around 100 drivers stuck on a major trunk road in Cornwall.
The South West is worst affected - with teenage students at one college in Bodmin having to stay there overnight.
The freezing weather is moving across southern England and Wales, affecting Wiltshire, Hampshire, Sussex and Kent.
There are warnings of rail delays and flights cancellations into Friday morning.
The Met Office has warned of "treacherous driving conditions" in some southern areas.
There are two yellow warnings in place for snow and ice for large parts of the UK, lasting until Friday afternoon.
Snow depths of 12cm (5in) have been recorded in Bodmin, Cornwall, the Met Office said. Parts of Cumbria have seen 8cm of snow, while there was 7cm recorded in Inverness-shire and 5cm in Powys.
Disruption also includes:
Dozens of schools in the county will be closed on Friday, while students at Callywith College have been forced to stay overnight
Transport for London had advised commuters to try to finish their journeys by 21:00 GMT due to warnings of ice, sleet, snow and windy conditions
British Airways has warned that some short-haul flights to and from Heathrow Airport on Friday morning have been cancelled or merged
Southeastern Trains has introduced a winter timetable for Friday morning and South West Railway has warned of cancellations as tracks are cleared
Newquay Airport was closed due to the snowstorm but has now reopened
Some schools in Wales closed early and others have announced they will be shut on Friday
Chepstow Racecourse has also cancelled Friday's meet
What's the forecast?
Up to 10cm of snow is expected in parts of the UK with snow depths of 5cm (2in) already recorded in Cornwall and Mid Wales, the Met Office says.
Further snow is forecast overnight into Friday, with 5-10cm (2-4in) expected in Wales and south west England.
In other parts of southern England, there could be 1-7cm (up to 3in) of snow.
BBC Weather presenter Stav Danaos said very heavy snow caused disruption for Thursday evening's rush hour across the south west of England.
Mid and south Wales, central and southern parts of England, and south east England are seeing the worst of the weather.
The north east of England and north Scotland will also see snow showers and cold temperatures on Thursday night.
Temperatures fell to their lowest level this winter, with Braemar, Aberdeenshire, dropping to -14.5C (6F) on Thursday evening.
This is the lowest in the UK since 2012 - when temperatures fell to -15.6C in Holbeach, Lincolnshire.