Met Office forecasters have issued a yellow weather warning for fog, with flights potentially facing cancellation across a massive swathe of the UK
The Met Office has issued a new weather warning for severe fog.
The yellow warning comes into force at 6pm today and will last until 11am on Monday, covering huge areas in England and Wales.
Visibility could drop to 50 metres or less in some areas, the national weather agency has said. There is also a risk of flights being delayed or cancelled, while bus and train services may also be impacted.
"Give yourself the best chance of avoiding delays by checking road conditions if driving, leaving extra journey time, or amending plans if necessary," the Met Office added. "Make sure you know how to switch on your fog lights, and check they are working before setting off on your journey."
Fog patches will form from Sunday evening and develop overnight, becoming "extensive" by Monday morning, the forecaster said.
Visibility plunging to 50 metres could cause significant disruption at airports, with the Met Office explaining that fog can force air traffic controllers to increase the distance between aircraft as they land. This reduces the number of planes an airport can handle, potentially causing delays and cancellations.
According to the forecaster, fog is officially recorded when visibility drops below 1,000 metres - but conditions can become far more severe, with dense fog reducing visibility to less than 100 metres.
Road, rail and ferry travel may also be disrupted, with passengers urged to check the latest travel updates before setting off.
The Met Office also warned motorists to slow down before entering fog, and to keep a bigger distance from any cars driving in front of them.
The fog is expected to ease slowly later on Monday morning.