Deep all day shade is best but....I don't have much of that.
This has worked very well to keep heat stress/stroke at bay:
I give a dose of
Sav-a-Chick electrolytes/vitamins about once a week during heat waves.
It
really seems to help....started this after they saved a heat stroked hen once.
Can mix up a smaller amount, just wrap the packet tight and store in a dry cool place.
Always have plain water available too.
BIG(9x14x2") chunks of ice last all day for wading, sitting, and sipping.
Much more useful to the chickens than frozen foods and treats.
Make space in your freezer!