The warning is valid from 7.00pm on Monday to 12.00pm to Tuesday.
“Areas of fog, some of it dense and freezing, will develop during Monday evening and overnight, persisting into Tuesday morning in places,” said the Met Office.
“Visibility may dip below 100 metres in some locations.
“Fog will tend to lift into low cloud in many areas on Tuesday, though a few spots may stay foggy into the afternoon,” concluded the Met Office.
Temperatures in London are also set to drop below freezing over the coming days.
Londoners should expect feel-like temperatures will drop to 0°C overnight.
Wednesday will see temperatures return to normal for this time year however things will turn cold again on Thursday when feels-like temperatures will dip to as low as -4°C.
London & South East England weather forecast
Monday January 17 to Friday January 21
This Evening and Tonight:
Areas of mist and freezing fog will form readily through the evening, with some dense patches developing during the night. Some clear spells overnight, with a sharp frost in places. Minimum temperature -3 °C.
Areas of mist and fog are likely to prove slow to clear, perhaps persisting all day in some spots. Otherwise, some sunny spells developing but further cloud moving in later. Maximum temperature 9 °C.
Outlook for Wednesday to Friday:
Unsettled Wednesday, with light rain moving south. Brighter and colder conditions will follow, with more settled conditions re-establishing for the remainder of the week, giving frosts and risk of fog.
(Source: The Met Office)