There are pros and cons to September.Pros...the weather would be great for those driving in from west of the Mississippi...Cons... Number one, if this is going to be a "family" trip, most schools start in September. Number two,it might be a financially worse time to go due to school shopping... Number three, i just checked the weather up there, mid 60's during the day, low-mid 40's at night...BURRRRRRRR. If in October, the Northern folks will most likely be looking at snow conditions before leaving. I think August would probably work better...My 2 cents