A good way of gauging the amount of discounts and crowd levels is to think of school or no school.
If schools have breaks during the year, and summer off, expect crowds to be higher and less discounts. It is not just kids off from school, but teachers, school administration, etc., that cannot take off during time when there is school.
So starting in early June, as soon as schools are letting out, you see less and less discounts and crowds go way up.
When kids in the Northeast start to go back to school in late August, the crowd levels start to go down and there are discounts until the Thanksgiving break starts.