For the first time in a month, mine were NOT panting and even ventured out of the coop. It's been high 90s with high humidity for a month and mine had gotten to where they would not leave the coop it was so hot. The coop is a 100 year old coop/hen house and it stays naturally cooler but I also added a fan recently because the flies and gnats were getting so bad in there since no one was going out. My birds have total run of the farm so to see them all staying in the coop is very odd. In any event, we had a cold spell come through today - it rained and temps dropped and had a nice cool, almost cold, breeze blowing all day. Thank you Lord. Everyone felt frisky again and went outside to forage. The coop got a clean sweep of flies and gnats.
The only other thing you can do other than fans and cool drinking water is to use shallow pans of cool water that they can stand in. Mine love to stand around in the cool water as if waiting for their pedicures.