The Met Office has issued a yellow warning on fog this morning, and dozens of flights have been cancelled out of London airports as a result.
There is also no Woolwich Ferry service running and no Thames Clippers at Royal Arsenal Woolwich because of the weather.
"Areas of fog, with visibilities locally below 100m, will continue to affect some eastern and southeastern counties of England until later this morning," the Met Office said.
"This may cause localised disruption on roads and perhaps delays at some airports, before gradually lifting and clearing from the south."
The Met Office added: "Visibilities are quite variable, some locations staying largely fog free, others seeing notably poor conditions."
The weather service said the lack of visibility was caused by moist chilly easterly drift which is leading to a lot of low cloud and fog this morning, some over the hills and some at low levels too.