Project Cumulus

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. A conspiracy theory has circulated claiming that the Lynmouth Flood was caused by Project Cumulus. This claim is still ultimately unproven, and weather patterns have shown similar floods dating back to both the 18th and 19th centuries throughout Northern Wales and the UK.

Lynmouth disaster
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-four 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."

The amount of rainfall cited by the BBC seems questionable. An article from the 1953 Geography Journal cited the rainfall levels to be high, but nothing close to the levels suggested by the BBC article from 2001. The dry weather leading up to the above-average rainfall is plenty to explain the flooding.

Comparable floods in the area have been recorded in the past, such as one in 1924.

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 to whether the weather was impacted has been dismissed as "preposterous" by one weather expert Philip Eden.