Working with the concept of thermal mass is also one of the most important things we can do in terms of trying to help our hens be comfortable during high heat. In the above pic, you see the back portion of the coop, which is west facing. While we do have a bank of trees and high shrubs, the reality is that during the highest heat portion of the late afternoon, the sun will cook the area directly bordering the west facing portion of the cook. This heat will build up in the earth (and especially surrounding pavement), and later the stored heat will radiate back up.
With night time temperatures slated to be 80-90F for most of the night, the last thing we want to do is extend the duration of heat exposure the coop and the hens get.
Working with thermal mass is a great passive heating or cooling method for building architecture, but a nightmare if not properly dealt with for live stock. In this case, a back yard umbrella has been set up to provide a buffer which will keep the immediate ground around the coop from accumulating too much heat. While it's not fool proof, this small shade buffer will later radiate whatever accumulated cooling energy it has to offer. At dusk or just after I will run a sprinkler for a short time, which will further cool the ground and radiate this back.
The other thing I will do in the early evening after the hens retire to the coop, is I will throw open every available coop door, and stay near the back portion of the house. While I believe the pomeranian early warning system largely dissuades most raccoons from trying to take a chicken again, I think being cautious is wise in this case. Trying to let in as much of the meager cooling air as we can, helps the chickens better weather when I lock down the doors of the coop at midnight.
Keep in mind that most of these methods will work great for us in the Pacific Northwest. Take what can be useful for you in your region, and adapt it as best you can to keep your flock comfortable.