As General Dwight D. Eisenhower prepared for D-Day, he needed a forecast. The new movie Pressure shows the tense make-or-break weather prediction that led to the successful invasion of Europe that spelled the beginning of the end of World War II If it weren't for a weather forecast, D-Day—the largest seaborne invasion in history—would have taken place on June 5, as originally planned. And if that had happened, the invasion would have ended in disaster.