Hello! i help organize and run several events here in Arizona and attend many more. In my opinion this is a loaded question and the best answer I can think of is that it depends in where you live and the agenda of the event. Here in Arizona there are a quite a few right at the end of summer and many more travel from out of town to the events and more as the weather begins to cool. in general you don't want to compete with other events relating to technology even if they seem to be "non-compete" because you force your potential audience to decide which can reduce your attendance..and you will also lose the opportunity of having that other host attend your event. I hope this helps a bit. Please submit more questions :)

Can't help other than to tell you personal preferences

February ....days are long, sometimes cold, easy destination tack on if located somewhere fun
Early June as ppl looking for mid year idea boost
Avoid summer
October best month in fall

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.