Our weather here in Oklahoma has already reached into the 90's. I can tell already, that my birds prefer cooler temps, and the worst is yet to come. I have a double door system for my human walkthrough door. A solid wood door, and then I can open it up, and I have one I framed with 1X3 pine with chicken wire. I open the solid wood one each day, and it funnels a breeze through the coop. In the middle of the day, I'll find my 9 birds laying in the shavings in front of the chicken wire door. I think they like the concentrated air movement.
I also allow my birds to free range already, (7weeks old) and during the hot weather, they usually stay in the run. The evening time is when they really prefer to range outside.
As for the birds being scared of too much wind, I think I might agree with that. I think they feel as though they can't focus on flying predators either by sight or by sound. That may be why they are hanging out inside.