As of Wednesday morning, dense fog enshrouded the city of London.
The thick fog rolled into the region around midnight local time and lasted through mid-morning, creating heavy traffic delays during the morning commute.
For five hours, the city had zero visibility conditions, and for nearly eight hours, visibility was down to 1/8 mile.
By Wednesday afternoon, more than 800 arriving and departing flights were cancelled or delayed at London Heathrow Airport, according to FlightStats data.
While this time of year is favorable for fog across the Northern Hemisphere due to longer nights and more time for morning fog to form, weather conditions in the city late Tuesday evening were prime for fog formation.
"Clear skies and calm winds are the main causes of fog," said AccuWeather Meteorologist Dan DePowdin said. "Wind yesterday was out of the southeast so that helped bring moisture to the area."
Moisture, clear and calm skies are the perfect combination for this kind of all-encompassing fog.
Although London is not expected to have another fog incident again this week, but instead some stormy weather is in store for the city.
The River Thames and Westminster Bridge in today's mist and fog. #london #photography pic.twitter.com/yGDpE9T8aj— Richard Eaton (@WorldCityPhotog) December 11, 2013
A foggy morning this morning, with a hint of sun coming through! ❄️ #fog #sun #london pic.twitter.com/U6Fvbpkzrv— B London Boutique (@BLondonBoutique) December 11, 2013