We had the iRV2 National Rally in Amana Colonies last summer:
Here are is the photo thread:
I didn't get to go but the week of the rally they had a massive heat wave with temps above 100 the whole time (this was in September too). The week before and week after were both great temps, go figure! Other then the heat, I think everyone really enjoyed the shops, factory tours, plays and other regional attractions. It seems like a fairly popular RVing destination.