moving chicks into coop in heat of summer

[laurabates]

I'm a new chicken momma, I have 23 chicks total. An array of Golden Buff, Buff Orpington, Barred Plymouth Rock, Australorp, Silkie, Easter Egger, Olive Egger, Brahma Bantam, Golden Campine, and Double-Laced Barnevelder. My girls were hatched on July 11th.
I live in Oklahoma, the summers are hot and humid. During the day the temperature hovers around the high 90's, at night it drops into the 80's.
My ladies are currently in my brooder and taking daily trips into the yard to enjoy the bugs and grass. I would love to move my girls into the coop as soon as I can :/ I've read that they need to stay in the brooder until they are fully feathered, so they can regulate their body temp.
But, since it's so hot out, would it be ok/safe for me to move them out into the coop at 3 weeks of age? At what point is it safe to move them into the coop in the heat of the summer?
If I do move them into the coop when they are 3 weeks old, what would I need to do to make it safe for them?

Thanks

 

[azygous]

They can't lose body heat when the outdoor temp is so close to their natural body temp, regardless of feather development.

Move them out!