pea soup fog

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Last updated

July 22, 2026

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"Pea soup fog," also known as a "pea-souper," refers to a very thick and dense fog. This type of fog is not a natural atmospheric formation but rather a result of pollution. It occurs when water vapor condenses onto airborne particulates, creating dark, heavy clouds that significantly reduce visibility.123

Historically, London was particularly known for these fogs, especially during the 19th century and into the 20th century, often exacerbated by the burning of coal for industrial and domestic purposes. The term "smog," a blend of "smoke" and "fog," emerged to describe this polluted haze. The Great Smog of London in 1952 was a severe instance, lasting five days and causing thousands of deaths due to respiratory illnesses, prompting significant environmental legislation.3

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Great Smog of London
Background
Known as “pea-soupers” for their dense, yellow appearance, such all-encompassing fogs had become a hallmark of London by the 19th century. But polluted fog was an issue in London as early as the 13th century, due to the burning of coal, and the situation only worsened as…
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Known as “pea-soupers” for their dense, yellow appearance, such all-encompassing fogs had become a hallmark of London by the 19th century. But polluted fog was an issue in London as early as the 13th century, due to the burning of coal, and the situation only worsened as…
Read More