We discovered that off season is whenever Florida schools are in session. We went to Disney two summers in a row (my parents live in Florida). We went to the Magic Kingdom on the same day of the week both years, but the second year was exactly one week later in August than the previous. That second year was about 40% less crowded than the previous. When we asked around, everyone told us that the difference was that Florida and Georgia schools were in session. I never would have thought, but locals have everything to do with crowd levels at Disney!