We've been over 110 here several days over the last couple weeks.
I try to keep cold watermelon, canteloupe, etc to give them during the day, but the main 'cooler' I have for them is to spray the coop down at least twice during the day (more often if I can). They don't like to be sprayed, and will run and hide in the hen house (which I also spray down). I try to spray the area down in the evenings after chores, too. It stays fairly warm in there for them at night, and that last spray down seems to make a big difference.
They have a couple not-so-big shade trees that help some.