1. I wouldn't worry too much until the temps hit mid 90's with high humidity. This combo seems to be when I may loose a bird or two and usually its an older bird.
2. Plenty of shade.
3. Plenty of fresh water and make sure that its in the shade all day. Hens don't like to stand in the hot sun to drink.
4. I will spray the run with water in very hot weather.
5. I use fans in the windows. I have four windows so I put the fans so they blow out, to draw out the heat and draw in the cooler outside air. Now when its almost as hot outside as its inside you would think it would make difference but it does create air flow over and around the birds which helps.
Approximately 7 years ago we had a stretch of heat that hit the 100's for a couple weeks. I actually would fill a 5 gallon bucket of water and "dunk" the hens in it. I would just pick them up immerse them until the water rose over their backs. I held them there for 30 seconds or so. It really did help cool their body temp down for a while. I think it help them cope, gave them a small break from the extreme heat.
I had about 20 birds then, it took time and most put up a fuss but it was for their own good.