The weather service has issued a yellow warning for fog covering London and south-east England, east and west Midlands, Norfolk and Hertfordshire in the east of England, parts of Yorkshire and Humber as well as parts of north-west and south-west England.
In Wales, the alert covers areas around Flintshire and Wrexham.
“Fog will slowly lift and clear during Sunday morning; likely slowest across parts of the West Country and central southern England,” the alert read.
The warning means travellers could face slower journey times with delays to bus and train services possible, while there is also a chance of delays or cancellations to flights.
Met Office meteorologist Tom Morgan said fog features “quite heavily in the forecast through this weekend and for some of us into next week, too”.
He puts it down to “a large area of high pressure dominating the UK for several days now”, while there has been “very little in the way of a breeze”.
Mr Morgan forecast a “cold and murky” start for many areas on Sunday, with “fog lingering through the morning across more southern parts of the UK in particular and perhaps even into the afternoon in some valleys, particularly the Severn Valley, down towards Worcestershire and Wiltshire”.
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Travellers are advised by the Met Office to give themselves the best chance of avoiding delays by checking road conditions before leaving, if driving, as well as allowing extra time for the journey and changing plans if necessary.
The fog is expected to largely lift after 10am, revealing a brighter spell in many areas than in recent days.
The agency said drivers should also make sure they know how to switch on fog lights, and check they are working before setting off and check how aeroplane, bus, train and ferry services are running before leaving, if using them.
Later this month, there is a chance of a polar vortex hitting the UK, bringing with it a sharp drop in temperature and the possibility of wintry weather.
