We experimented a lot with the timing of tech and Entrepreneurship related events and early September would consistently bring us the highest quality of attendees.

Investors and senior partners generally do not like to travel during summer months and spend that time with their kids instead so they start traveling (enthusiastically) again in September once the kids are back in school.

Same goes for students, you will attract dramatically more students when the school is in session than during summer or winter breaks.

Source: I organized few conferences in the Atlantic region.