Heathrow Airport has cancelled 80 flights as it prepares for possible snowfall later on Thursday.
The national hub, which has apologised for the disruption, said in a statement: ''The latest forecast is for snow this afternoon, which will reduce the number of aircraft able to take off and land each hour.
"Alongside our airline partners and NATS, we have taken the decision to reduce the flight schedule on Thursday, to allow airlines to rebook passengers onto un-allocated seats ahead of time where possible."
British Airways said it was "refunding or rebooking any affected customers onto alternative flights".
Gatwick Airport said it was cancelling four flights.
Wintry conditions have also caused travel disruption further north.
The chief meteorologist at the Met Office, Paul Gundersen, said most snow was expected in northern and western Scotland, Northern Ireland and around Irish Sea coasts.
Yellow, "be aware" warnings of wind and snow have been issued by the Met Office for Scotland.
On higher ground, there could be between 10 and 20cm of snow.
The ferry operator Caledonian MacBrayne has warned of "heavy disruptions".
Northlink ferries and Orkney Ferries also said the weather was likely to cause difficulties.
In Northern Ireland, there was thick snow in Coleraine and Ballymena.
Mr Gundersen said the "situation over the southern half of England is more complicated".
"Southern counties of England and Wales can expect a cold and wet day with some heavy rain on Thursday, but there's an increasing chance this will turn to sleet or snow, especially over hills, during the afternoon and evening," he said.
"There is a chance of snow settling, bringing disruption to transport during the evening rush-hour and possibly interruptions to power supplies - this more likely across East Anglia and south-east England."
He added: "As skies clear on Thursday night, it is likely to become icy in many areas."
The north of England was one of the regions that saw the worst of yesterday's weather, with gusts of up to 93mph recorded at High Bradfield in South Yorkshire and 82mph at Emley Moor in West Yorkshire.
Around 3,000 homes and businesses in Scotland, Northern Ireland and northern England were also without power during the day.
In Scotland, motorists faced long delays after a lorry blew over on the Forth Road Bridge at 2am.