The Met Office has extended its yellow warning for fog, affecting London and the south east, and said misty conditions will continue throughout tomorrow morning.
Fog is expected to develop over parts of Southern England through Thursday evening and overnight, according to the weather forecasting service.
The Met Office said the fog will then "only slowly clear during Friday morning".
Hazardous driving conditions and slower journey times can be expected and delays to bus and train services, plus delays or cancellations to flights are possible, the Met Office warned.
Flights in and out of Heathrow were affected on Thursday, with the airport confirming via Twitter that some planes have been delayed due to weather conditions, and at least one flight diverted to Gatwick.
Hi Jeff, yes we are experiencing some delays due to the fog. Thank you— Heathrow Airport (@HeathrowAirport) November 2, 2017
Flights in and out of London Gatwick may also be affected by the fog.