Is there anything special you do to keep your chickens cool? The heat and humidity has been horrific. There are fans in both coops, windows and doors have heavy screen so they are open at night. I add ice, several times a day, to their water buckets and use electrolytes daily. I buy "seconds" from the veggie & fruit stand (my garden only has zucchini ready) and keep it in the fridge to give them during the hottest part of the day. We did get a break in the weather today, they seem much more comfortable.
I'm in zone 9. It is hot and humid about 8 months of the year. I don't do anything special for cooling. I have a fan in the coop area, but my chickens free range so they are only in there at night. I guess they just become acclimated.
I gave mine ice water when I first got them, but I work all day so that melted before it really got hot. It got hot so fast this past week or so that several of my watermelons split. Rats! So the chickens to those (they loved them and can't wait for more to split).
porkpal is right, after the first year mine just seemed to acclimate.
If there is no seen threat in the area, ours are allowed to free-range most daylight hours. There is ample shade for them to laze about in. Some, I have noticed, enjoy standing for short periods in a shallow container of water that I provide for them in a shaded area.
If they are to remain penned through the heat of the day, I will often pour a bucket of water in their pen so they will have damp earth on which to dissipate body heat.
Construct coops/pens with generous square footage and height and orient them to maximize the prevailing summer winds in your area (SSE here).
Easily controlled and very important, I think, is your flock not be too fat.