Project Cumulus

Operation Cumulus was a project of the UK government in the 1950s which was investigating weather manipulation, in particular through cloud seeding experiments. Known jokingly within the project as Operation Witch Doctor, the project was operational between 1949 and 1952.

Motivation
The military were controlling the weather for several reasons, as detailed in minutes of an Air Ministry meeting held on 3 November 1953. They included:
 * "bogging down enemy movement";
 * "incrementing the water flow in rivers and streams to hinder or stop enemy crossings";
 * clearing fog from airfields.

The Lynmouth disaster
On 16 August 1952 a severe flood occurred in the town of Lynmouth in north Devon. 9 inches (229 millimetres) of rain fell within twenty-four hours and the East Lyn River rose rapidly and burst its banks. Thirty-four people died and many buildings and bridges were seriously damaged.

Conspiracy theorists speculate that Project Cumulus contributed to the conditions that caused this flood, but evidence was never found. A few days before the disaster a seeding experiment was carried out over southern England. Alan Yates, an aeronautical engineer and glider pilot who was working with the operation, sprayed salt in the air and was "elated" to learn of a heavy rainfall in Staines shortly after. Conspiracy theorists claim that there are rumours that official documents were deliberately destroyed and that certainly some classified documents are missing.

Experts however deny that the experiments could have caused the accident. Meteorologist Philip Eden claims that "it is preposterous to blame the Lynmouth flood on such experiments".