I let the flock out to free range in the mornings when it's cooler, and make sure they get a good start on their feeding at that time. When it starts getting really hot around noon, I move them to a tractor parked in the deepest shade in the yard, covered with shade tarps. Every hour or so after that, I let them out of the tractor while I hose it down and get the ground good and wet, replace the water with cool, fresh water, and put them back in the tractor. Any chicken that's panting really hard gets brought indoors for a half an hour breather in our indoor bird room that's kept at around 82 degrees. So far, that's only been our feather footed girls. The other chickens seem to be handling the heat ok.
One hen, the smallest one, has kept chugging along laying eggs all throughout this heat, never missing a beat. The other two stopped for a few days but are now laying again.