Photos and videos from the worst-affected areas show streets and cars blanketed in white, leading to concerns about health and safety on treacherous roads.
Up to 20cm of snow could fall in the hardest-hit areas of Scotland, the Met Office said this morning, warning travel disruption is possible.
Some more rural parts of the country could see their power supplies and mobile phone coverage affected, according to the Met Office.
A yellow warning for snow and ice for North West England, Yorkshire and Humber, and northeast England was put in place at 8am on Wednesday and remains in force until 9pm on Thursday.
Footage from Halifax shared on social media shows a bus skidding down a hill on an icy road as snow falls heavily.
Yeah, I think I'll walk home. 😱
It is treacherous out there right now! The bus driver definitely regretted attempting this on Bank Bottom over in Halifax 😬🌨️ #uksnow #snow #Yorkshire pic.twitter.com/dJvRVswBcm
— Lockdown Leeds+ (@LeedsPlusSocial) January 14, 2021
The weather led the Yorkshire Ambulance Service to declare a major incident on Thursday afternoon after heavy snow and a surge in patient demand hit the region.
Some snow fell overnight in northeast England, where residents in the Gateshead and Durham areas woke up to a blanket of the white stuff.
Forecasters say snow will give way to rain and sleet as the day progresses, with temperatures becoming milder by lunchtime.
Further south it is a much wetter picture. Heavy rain is forecast for London, the southeast and coastal areas.
Northern Ireland and Wales are also expected to stay mainly dry.
Looking ahead to Friday, it is expected to be a dry but chilly start to the day for most, with areas of low cloud and fog, especially in some eastern parts.