In Southern California where we live, it has already been up to 100 and summer hasn’t begun. We have a hardware cloth covered geodesic dome as the chicken run with the coop inside. We have sand inside the dome and coop and grape vines growing over the top of the dome. When the temperatures climb, I turn on the misters to lightly moisten the sand and have a fan outside the dome blowing in. The chickens freak out when the misters are on so lately I’ve been just watering the sand with a watering can and then raking the sand into little pyramids for my girls to kick around in. I have two large sheets of white plastic cardboard as a shade awning which also works great to keep areas dry when it rains all 3 days out of the year here

We installed a mini A/C in the coop and run it on the super hot days especially during egg laying time so my girls aren’t over heating in the nest boxes and sometimes at night on a timer to cool off the coop. We went a little overboard on insulating the coop to keep it nice year round- I think our coop is better insulated than our house.

We also have thermal blackout curtains to keep the heat and sun out of the coop on the east/west windows.
I use the reflective car windshield panels in strategic locations to make even more shady areas. The great thing with the dome is that I can use magnets to hold up the sun shields and thermal curtains.
I feed my girls cold watermelon in a tray that is actually a catlitter pan for older cats. It’s weighted and has a lower edge on one side so my bantams can get into the tray too. I have 5 waters all around the shady areas of the dome; 2 with plain cool water that I replace mid-day and 2 with electrolyte formula. The 5th waterer is camomile tea which is usually the first to be drank down.
On really really hot 100+ days, I bring my bantam silkies in the house and they go into a kiddie pool with sand and a playpen around it. My Roo goes into our basement set up with perches, mirrors, plush ‘girlfriends’ and food/water placed on a large dog crate tray to catch spills.
The rest of the chickens go into the coop and enjoy the A/C for a few hours just to get a reprieve from the heat, but since we don’t have much humidity here we pretty much keep everyone cool with shade, deep moist sand and a box fan. Something to keep in mind with wet sand is that you really need to scoop out the chicken poops before you moisten the sand or it’ll be like fly city. The box fan helps somewhat with keeping flies away. I use a kitty litter scoop to sift out the poo each time I go in the chicken dome. It’s a little bit of work each time, but it’s worth it cumulatively and nice to be able to walk bare foot in the dome without stepping in poo. You also get an idea of how cool your birds are when you can feel with your feet how nice the sand feels, it’s easy enough to hose off your feet afterwards.
My first year having chickens really stressed me out on how to keep them cool during our hot dry summers, but I think I’ve finally got it dialed in for most days with the deep lightly damp sand, shade (white plastic cardboard, thermal reflective cloth, car sun shields, and grape vine leaves) and a simple box fan. Hope some of these ideas help.