The planning team responsible for the invasion of Normandy had to consider the weather, the moon and tides when assigning a date for D-Day. Air operations required clear skies and a full moon for good visibility. Naval operations required low winds and calm seas to safely transport troops ashore. Ground troops needed to land at low tide, when German beach obstacles were exposed and easier to deal with.
D-Day required the best combination of these factors. Military planners relied on information from meteorologists and other specialists, who advised that D-Day should fall somewhere between 5 and 7 June 1944. D-Day was set for 5 June, but Supreme Commander General Dwight D Eisenhower knew that the weather could be critical in determining whether the invasion went off as planned.
