Well, I have been involved with the planning of a ZCON. As you mentioned before, it's mostly about the track day. When the rest of the committee suggested October for the 2018 convention, I thought they were bonkers. However, I was COMPLETELY wrong. It just so happens that October is about the least rainy month in the Atlanta area. Z1 Motorsports was also generous enough to run the track day and People's Choice show for the convention when they normally would have held ZNationals. Yes, they got a cut of the convention proceeds, but I suspect it was less than they usually clear on ZNationals.
The end result was that we had a great turnout for ZCON 2018. It was an incredible undertaking that I never wish to attempt again. 🙂
ZCON 2020 was a little different. Covid was threating the convention, but just before the ZCCA threw in the towel, Nissan approached them about the debut of the new Z. The convention was in September, and the pandemic kept the attendance down some. It was nice having it in September instead of the middle of summer. The weather actually started cooling off quite a bit around the time of the People's Choice show on Saturday.
After attending two cooler month ZCONs and 3 VERY hot ZCONs, I certainly prefer the milder weather.