The London Marathon, Dedicated To The Olympic Games In 2012

Snow is relatively uncommon, particularly because heat from the urban area can make London up to 5 °C (9 °F) warmer than the surrounding areas in winter. Some snowfall, however, is usually seen up to a few times a year. The February 2009 Great Britain and Ireland snowfall was the heaviest London had seen for 18 years.
London is in USDA Hardiness zone 9, and AHS Heat Zone 2. Although extreme weather does not happen very often, deep depressions have been known to pass through like the Great Storm of 1987. Tornados are rare, but the Kensal Green area of the city was hit by the 2006 London tornado causing £10 million of damage and injuring 6 people.
In the second half of the 19th century and the first half of the 20th, London was noted for its dense fogs and smogs. Following the deadly Great Smog of 1952, the Clean Air Act 1956 was passed, leading to the decline of such severe pollution in the capital. In 2010, the City of London was ranked as one of the most polluted places in Europe.