|Birth name||James Martin Stagg|
30 June 1900|
|Died||23 June 1975(aged 74)|
|Service/branch||Royal Air Force (Royal Air Force Volunteer Reserve)|
|Years of service||1943-1945|
|Battles/wars||World War II|
|Other work||Director of Services at the Meteorological Office|
Group Captain James Martin Stagg, CB, OBE, FRSE (30 June 1900 – 23 June 1975) was a British Royal Air Force meteorologist who notably persuaded General Dwight D. Eisenhower to change the date of the Allied invasion of Europe in World War II, from the 5th of June to the 6th of June 1944.
Stagg was born in Dalkeith, Scotland to Alexander and Ellen Stagg. In 1924, he became an assistant in the British Meteorological Office and was superintendent of the Kew Gardens observatory in 1939. In 1940, he married Elizabeth Nancy Kidner; they had two sons, Scotland rugby player Peter Kidner Stagg (born 1941) and Alexander Martin Stagg (born 1944). In 1943, he was commissioned a Group Captain in the Royal Air Force Volunteer Reserve and appointed the chief meteorological officer for Operation Overlord. Stagg was the senior staff meteorologist working with input from three separate forecasting teams from the Royal Navy, Met Office and USAAF. The detailed history of the forecasts is subject to disagreement in the accounts published by participants, including Stagg himself.
Stagg later worked as director of services at the Meteorological Office until 1960.
For his invaluable services during the planning of D-Day, Stagg was appointed an Officer of the US Legion of Merit in 1945 and was also appointed Officer of the Order of the British Empire (OBE) at the same time. He was appointed Companion of the Order of the Bath (CB) in the 1954 New Year Honours. He was elected as a Fellow of the Royal Society of Edinburgh in 1951 and elected as president of the Royal Meteorological Society in 1959.
- "James Martin Stagg (British meteorologist)". Encyclopædia Britannica. 2013. Retrieved 22 September 2013.
- Fleming, James R. (2004). "Sverre Petterssen, the Bergen School, and the Forecasts for D-Day" (PDF). History of Meteorology. International Commission on History of Meteorology (ICHM). 1. Retrieved 7 August 2006. citing
- "No. 37300". The London Gazette (Supplement). 9 October 1945. p. 4958.
- "No. 40053". The London Gazette (Supplement). 1 January 1954. p. 4.
- Imperial War Museum (1995). "D-Day: The role of the Met Office" (PDF). Retrieved 20 April 2013.
- Met Office. "70th anniversary of the D-Day landings and the role of the Met Office". Retrieved 10 October 2015.
- "Analysing and forecasting the weather of early June 1944". European Centre for Medium-Range Weather Forecasts. 7 July 2004. Archived from the original on 4 October 2006. Retrieved 3 August 2006.
- "Remarks by Chief Justice William H. Rehnquist to the American Meteorological Society, 23 October 2001". Retrieved 3 August 2006. (Rehnquist served as a USAAF weather observer in World War II.)
- Slater, Herschel (1 June 2004). "Weather forecast helped commander make D-Day decision". Chapel Hill News, North Carolina State University. Archived from the original on 13 March 2007. Retrieved 3 August 2006.