The Met Office has issued a yellow warning for dense fog until 11am on Monday which could affect commuters on their way to work.
Visibility could fall to less than 50m in places, making driving difficult. Bus, train, ferry and flight services could also face delays or cancellations.
The fog will gradually lift through Monday morning, although some patches could linger into the afternoon.
Commuters are also experiencing a chilly start, with temperatures widely falling into low single figures and ground frost likely in many areas.
Heathrow has advised anyone driving to the airport to allow extra time for their journey because “overnight fog has affected visibility on roads” in the area.
“We advise passengers to check with their airline before leaving home and to drive with care,” it said.
Thick fog caused a 30-car pile-up on the M20 in Kent, leaving two people seriously injured, as well as a 19-car collision on the A303 in Hampshire.
Fog will be more widespread than Sunday night as clearer skies across England and Wales allow heat to escape quicker, causing temperatures to fall.
Patchy fog could also develop outside the warning area in northern parts of the UK wherever skies remain clear for long enough.
Fog forms when air cools and water vapour condenses into tiny droplets suspended near the ground, creating cloud at ground level.
Visibility of 50m or less can cause severe travel disruption. The Met Office advises drivers to check road conditions before setting off and use fog lights when visibility is seriously reduced. Allow extra time for your journey and adjust your plans if necessary. Patchy fog can be particularly dangerous because visibility can change suddenly.
The RAC motoring organisation recommends allowing extra stopping distance between your vehicle and the one ahead.
AA president Edmund King said drivers need to be prepared to adapt their speed on the road, saying: “One of the biggest mistakes is simply following the rear lights of the car in front. It can give you a false sense of security and means you may be travelling too close to react safely if that vehicle suddenly stops.”
If you’re using public transport or flying, check for updates from your operator and follow its advice. Flights may be delayed because aircraft need greater spacing when landing in fog.
