James Stagg’s D‑Day Weather Forecast Enables Allied Invasion

Group Captain James Martin Stagg, the chief meteorological officer for Operation Overlord, delivered a decisive weather forecast on the evening of 4 June 1944. He told Supreme Allied Commander General Dwight D. Eisenhower that a brief window of tolerable conditions would open on 6 June, allowing the planned amphibious assault on Normandy to proceed. Eisenhower, after a period of silence, approved the invasion based largely on Stagg’s reading of Atlantic charts.

At the same time, Stagg’s pregnant wife, Betty, was in a London hospital ward enduring German bombing raids. Stagg was unable to join her, remaining at the briefing to finalize the decision that would involve 156,000 troops, thousands of ships, and the strategic direction of the Western Allied war effort.