Yellow warnings for snow and ice have been extended as cold weather continues to cause disruption across the UK.
The new alert for northern Scotland and north-east England could mean fresh snowfalls in those areas.
Motorists relying on cars during this week's rail strikes have been urged to "plan, prepare and consider" before setting off.
A critical incident has been declared in Shetland after a power cut left 3,800 homes without electricity.
Energy firm SSEN Distribution warned that many homes there will be without power until the end of the week as engineers face "extremely challenging conditions".
Shetland has been issued with an additional yellow weather warning with gusts of up to 65mph forecast for some parts.
Yellow warnings covering London, the south-east and south-west of England will remain in place until 10:00 GMT on Wednesday.
A band of rain moving in from the south-west of England may turn into snow as it reaches land overnight – the Met Office says that region could see up to 10cms of snow on higher ground such as Dartmoor and Exmoor.
Warnings for ice in Northern Ireland, the East Midlands and Yorkshire and Humber are set to end on Wednesday at noon.
The extended Level 3 cold weather alert issued by the UK Health Security Agency (UKHSA) covers all of England and is now in place until 09:00 GMT on Friday, 16 December.
As a result of that alert, people are advised to look out for friends and family who may be vulnerable, and ensure they have access to warm food and drinks and can heat their homes adequately.
Temperatures fell to a low of -17.3C (0.8F) in the early hours of Tuesday in Braemar in the Scottish Highlands – making it the UK's coldest night since February 2021.
Braemar looks set to be the coldest spot in the UK for a third night running with temperatures as low as -10°C. Forecasters says strengthening winds across Scotland may prevent temperatures falling as low as previous nights.
Only around 20% of rail services ran on Tuesday as members of the RMT union walked out over pay and conditions. Further strike action is expected on Wednesday, Friday and Saturday of this week.
This means many people will choose to drive to make the kind of journey they would normally do by rail – but in significantly more treacherous conditions than usual due to the cold weather.
Rod Dennis from the RAC said the service has been experiencing record demand from drivers – he described Monday as the "worst-ever winter breakdown cocktail" with around 12,000 drivers needing help, the equivalent of eight every minute.
He added that Tuesday "remains an incredibly demanding day for our patrols" because more drivers are on the road due to the rail strikes.
In Scotland, police are warning drivers not to leave their cars while defrosting them after the theft of two vehicles in West Lothian.
The drivers had left their cars after switching them on to let the heaters defrost windows.
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Cold conditions continue across UK
Cold snap weather warnings extended across UK
The RAC has issued some tips for drivers to stay safe on the roads:
Find out the weather forecast for your area, with an hourly breakdown and a 14-day lookahead, by downloading the BBC Weather app: Apple – Android – Amazon
The BBC Weather app is only available to download in the UK.
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