Project Cumulus was a 1950s UK government initiative to investigate weather manipulation, in particular through cloud seeding experiments. Known jokingly internally as Operation Witch Doctor, the project was operational between 1949 and 1952.
- "bogging down enemy movement";
- "incrementing the water flow in rivers and streams to hinder or stop enemy crossings";
- clearing fog from airfields.
On 16 August 1952 a severe flood occurred in the town of Lynmouth in north Devon. Nine inches (229 millimetres) of rain fell within twenty-four hours: "Ninety million tonnes of water swept down the narrow valley into Lynmouth" and the East Lyn River rose rapidly and burst its banks. Thirty-five people died and many buildings and bridges were seriously damaged. According to the BBC, "North Devon experienced 250 times the normal August rainfall in 1952."
A conspiracy theory has circulated that the flood was caused by secret cloud seeding experiments conducted by the Royal Air Force. However, noting that the experiments were not secret, that the cloud seeding experiments were at the scale of individual clouds, and that the whole of the southwestern corner of the British Isles was affected by heavy rain at the time, the theory has been dismissed as "preposterous" by weather writer Philip Eden.
- Vidal, John and Helen Weinstein, RAF rainmakers 'caused 1952 flood', The Guardian, 30 August 2001, retrieved 21 July 2007.
- 1952: Flood devastates Devon village, BBC
- Rain-making link to killer floods, BBC, 30 August 2001, retrieved 21 July 2007.
- Hilary Bradt; Janice Booth (11 May 2010). Slow Devon and Exmoor. Bradt Travel Guides. p. 249. ISBN 978-1-84162-322-1.
- Vidal, John; Weinstein, Helen (30 August 2001). "RAF rainmakers 'caused 1952 flood'". The Guardian. Guardian News and Media Limited. Retrieved 12 July 2018.
- Eden, Philip. ""The day they made it rain" Lynmouth Flood man-made?". WeatherOnline. Retrieved 22 January 2018.
Any meteorologist with a rudimentary knowledge of cloud seeding could explain why it is preposterous to blame the Lynmouth flood on such experiments.