I lost one buff Orpington hen last summer in the middle of the VERY hot, VERY humid summer. We set strings of records last year, broke several record temp days, recorded the longest string of days above 90 degrees EVER for this region, and much of the summer was spent suffering through humidity levels of 80%.
Some tips for keeping them cooler are:
1. Have a dry area where they can dust bathe -- it really will help them keep cooler, plus will help naturally deter mites
2. make sure to keep their waterer clean and fresh (may require more than one water change per day) -- bacteria grow MUCH faster in warm weather. Tip: if the waterer feels "slick" or slimy, there's bacterial growth, and the waterer needs to be sanitized. You can use diluted bleach water; just be sure to rinse well. If you use ANY cleaner, rinse, rinse, and then rinse again. Many folks who use the plastic waterers use a tablespoon of apple cider vinegar (also known as ACV) to help keep down bacterial growth (most bacteria don't like an acidic environment) and to add beneficial vitamins & minerals. Use the unfiltered kind (the kind with the sediment in it). Don't use the ACV if you use the galvanized metal waterers, as the acidity will cause them to rust more quickly.
3. You can put some ice in the waterers in the morning or evening to make sure they have cool water for at least a part of each day.
4. Make sure they have access to some type of shade -- under a tree is fine, some use shade cloth or tarps for a protected area, and I
also put two small brush piles inside the run for some shade AND for a quick protected area in case an aerial predator pops by
5. Offer chilled or frozen goodies such as watermelon, cantaloupe, cucumbers, mixed frozen veggies, etc.
6. Mist an area of the ground (shaded will stay damp longer) so they can lay on the ground and cool off as the water evaporates
7. You can also put a low-flow sprinkler or mister in the run on a timer -- some of mine loved walking through the mist; others avoided it
like it was spraying them with acid! It was very much a personal preference with them.
8. Make sure your chicken house / coop has PLENTY of ventilation -- I kept a fan going in the chickenhouse window almost every night
Hope some of these tips will help you and your chickens rest more easily this summer!
ETA: and since I can't remember whether or not I greeted you when you joined
, in case I didn't, here's a somewhat belated WELCOME! from western Kentucky!