The Met Office say patchy fog is expected to form through this evening and into tomorrow morning.
Radiation fog occurs mainly in the winter, during clear skies and calm weather conditions.
James Madden, a forecaster for Exacta Weather, warned that snow will hit "northern and western areas" next week.
Pavements may also be affected, increasing injuries from slips and falls.
'Westerly winds will clash with colder air to deliver widespread and heavy snow showers across some large swathes of the country. Overnight fog and any frost should clear.
Mr Wilson said: "There is a lot of radiation fog around at the moment".More news: Legislators say they are close to CHIP deal
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The warning covers Northern Ireland, Wales, north-west England, south-east England, West Midlands, Yorkshire and Humber and south-east England. Lowest temperatures are expected to be 4° to 8°.
"Many parts" of Scotland are predicted to be hit by the wintry conditions at the start of next week, with the snow showers expected to be worst in the west.
"This results in a reduction of the air's ability to hold moisture which allows water vapour to condense into tiny water droplets eventually leading to the formation of fog".
Where is radiation fog in the United Kingdom?
"Elsewhere it will be dry with clearer spells".
Thick fog will also cause travel chaos across the United Kingdom as commuters will face hard driving conditions and flight delays today.