A yellow weather warning for "freezing drizzle" and fog has been issued for parts of England.
The Met Office on Tuesday night said the warning had been issued for London, as well as the south west and south east of England, and was officially in place until 8am on Wednesday.
The Met Office said "patchy freezing fog" over parts of Dorset, Somerset and Wiltshire would be dense at times overnight and would be "slow to clear" throughout Wednesday morning.
Areas stretching from Exeter to Oxford are set to be affected, with lows in that region of -5C recorded at Benson in Oxfordshire, Farnborough in Hampshire and Wiltshire's MoD Boscombe Down.
Visibility as low as 50 to 100 metres was likely in a few areas and some untreated surfaces could turn icy, resulting in "potentially difficult driving conditions".
Freezing drizzle is drizzle that freezes on contact with the ground. When freezing drizzle accumulates, it creates an icy layer.
This type of precipitation alone does not generally result in significant ice on the roads however owing to its light, low-intensity nature.
It can be extremely dangerous to aircraft in icy conditions, as the supercooled water droplets will freeze onto the airframe, degrading aircraft performance.
Commuters have been told to brace for delays both on the road and on public transport services. There was also a chance of delays or cancellations to flights.
The Met Office said residents and commuters in Bracknell Forest, Buckinghamshire, Hampshire, Oxfordshire, Reading, Slough, Southampton, Surrey, West Berkshire, West Sussex, Windsor and Maidenhead and Wokingham would need to be mindful of the conditions.
The fog was also due to hit Bath, Bournemouth, Christchurch, Poole, Devon, South Gloucestershire and Swindon.
Meanwhile, unusual weather has "flipped the norm" and left parts of northern Scotland enjoying warmer temperatures than southern England, the Met Office said.
An overnight low of -8.6C was recorded in Benson on Monday, with Altnaharra in northern Scotland a comparatively balmy 10.6C.
The Environment Agency has 23 flood warnings in place across England.