It gets even more incredible. The landings would have been canceled for the day they actually happened, except that the meteorology officer in Eisenhower's staff predicted that there would be a short break in the bad weather sufficient for the landings to occur.
Eisenhower rolled the dice and the weather did indeed hold up long enough for the invasion to occur. His opponent, Gen. Rommel, felt the weather was going to be so bad there was no way the invasion could commence so he was actually away from Normandy on D-Day to see his family.
http://www.history.com/news/the-weather-forecast-that-saved-...