A period of unusually cold weather, combined with an anticyclone and windless conditions, collected airborne pollutants—mostly arising from the use of coal—to form a thick layer of smog over the city.

[10][11] A period of unusually cold weather preceding and during the Great Smog led Londoners to burn much more coal than usual to keep themselves warm.

There were also numerous coal-fired electric power stations in the Greater London area, including Fulham, Battersea, Bankside, Greenwich, West Ham and Kingston upon Thames, all of which added to the pollution.

[17] Additionally, there was pollution and smoke from vehicle exhaust, particularly from steam locomotives and diesel-fuelled buses which had replaced the recently abandoned electric tram system.

[19][20] The resultant fog, mixed with smoke from home and industrial chimneys, particulates such as those from motor vehicle exhausts, and other pollutants such as sulphur dioxide, formed a persistent smog, which blanketed the capital the following day.

Wilkins (of the Department of Scientific and Industrial Research, whose measurements would make clear the connection between smoke, sulphur dioxide, and rising deaths), fog, white mist, or grimy smog covered "many parts of the British Isles", while "In London and the Thames Valley, fog or smog covered upwards of 1000 square miles".

[32] In February 1953, Marcus Lipton suggested in the House of Commons that the fog had caused 6,000 deaths and that 25,000 more people had claimed sickness benefits in London during that period.

[1][2][35] In the long term, individuals who were foetuses or infants at the time of the smog ended up having lower intelligence and worse respiratory health than their peers.

Central heating (using gas, electricity, oil, or permitted solid fuel) was rare in most dwellings at that time, not finding favour until the late 1960s onwards.

[44] An episode of The Goon Show entitled 'Forog', broadcast on the BBC Home Service 21 December 1954 was a thinly veiled satire on the killer fog crisis.

The script by Eric Sykes and Spike Milligan concerned the statues of London's monuments, who could get up and move about the city undisturbed only at times when it was enveloped in a characteristic smog.

The D. E. Stevenson novel The Tall Stranger (1957) opens with a dense "fog" that penetrates indoors and endangers hospital patients, in an apparent reference to the 1952 smog event.

Kate Winkler Dawson's book Death in the Air (2017) interweaves the story of the Great Smog of London with that of serial killer John Christie.