Northern California foothills see several days over 100 each year, sometimes we get a whole week in triple digits! Once the summer sets in, even our water is lukewarm out of the tap for the rest of the season! I just started dropping a pop bottle full of frozen water into the gallon chick waterers to keep their drinking water cool. It' easy, lasts all day and the bottles can be refrozen each night. We also have a mister hose on a manual timer so that I can go turn the mist on for 15 mins, or a couple of hours at a time. The misters will eventually moisten the straw on the floor of the run but the surface dries quickly (and the evaporation helps cool the ambient air for awhile after the misting stops), but it never gets "wet" because the timer shuts the mist off before saturation occurs.
I wanted to build under the shade of an oak tree out back, but it's too close to the neighbor (and his bb guns & his pit bulls) so I had to move the coop to the opposite end of the yard and they only get morning shade, but the afternoon sun just bakes that area :/ I do have shade screen & roll up shades on the west end of the run to provide shade, the coops west wall is solid wood but the other three sides are layers of wire with shade screen cloth over it for ventilation. The roof of the coop is white metal roofing and is pitched at a good angle to allow heat to rise and escape quickly.
We just had 9 chicks hatch 2 days ago & I'm a little worried about the fluff balls ... since this week is predicted to be triple digits for several days in a row. Mom decided to hatch & raise them on the floor of the secure run and I trust she knows which corner of the chicken fort is best suited to her brood so I'll just let her do her thing.