35. D-Day’s Tricky Weather
One thing over which Eisenhower and the Allied commanders had no control, but which could nonetheless wreck the carefully planned invasion, was the weather. For D-Day to stand a chance of success, there had to be a combination of conditions involving tides and moon at a specific time of the day. A full moon would help the parachute landings behind the beaches the night before the operation. On the beaches themselves, the first landing crafts should discharge their troops halfway between high and low tides, with the tide coming in. However, even with those conditions met, the weather still had to cooperate. Eisenhower scheduled the invasion for June 5th, within a narrow window of the right moon and tide conditions, but then the weather failed to cooperate.
Delaying the Mission
On June 4, 1944, one day before the scheduled invasion, a weather front moved in. It brought low clouds that would prevent airplanes from finding their targets, and rough seas and high winds that would prevent the launching of landing craft. Landing on the 5th was off, but by then troops had already embarked on ships, and vessels from the farthest staging areas were already sailing in convoys towards Normandy. By halting those ships in place, while hoping the Germans didn’t spot them, the invasion could be pushed back a day, to June 6th – if the weather improved on the 6th. Otherwise, the invasion would have to get pushed back weeks before the next window with the right tide (but not moon) conditions occurred on June 18-20, or a full month for the next window with both the right tide and moon conditions.
