June 6, 1944, might have been remembered as doomsday instead of D-Day if General Dwight D. Eisenhower's chief weatherman had been wrong about his forecasts.

When J. M. Stagg was appointed chief meteorological officer of the Allied Forces in October of 1943, he had no idea he would pay a crucial role in shaping world history. Little did he know it would be his analysis on which the U.S. Supreme Commander would base his decision to launch the Allied invasion on the beaches of Normandy.