We had Summer Rush and it was the biggest push. The biggest gatherings were the WaterSport Weekend party (lake house party) and the Around the World Party at the house.
We'd have the bulk of our class already setup and ready to go by the time school was back in. Then they do the actual "Formal Rush" the week before school starts. Much more structured, suits, speaches, blah.... We'd pick up a few there to finish out the class.
One of the Admission Counselors used to be a lil' Sister of the chapter; so we'd get the full list of incoming freshmen and their phone numbers from her