There are many ways to beat the heat with backyard chickens. One of my favorite ways is to give them this tiny wading pan.
We converted a drip pan by plugging the side hole up with a plastic cover.
For this to work you need to do a few things everyday.
Number one: is to empty it every night or every morning before your birds can access it.
This is very important, unless you have an enclosed run, other birds can access the water. Wild birds are known for carrying mites, lice or anything other parasites.
Two: Following that train of thought you need to clean it out everyday.
Three: Refill with fresh clean cold water every day.
Four: Place the water in the shade.
Five: Make sure the water level is under two inches. This is mainly for them to step in, cooling off their feet will really help cool them off - they will drink from it as well.
While the steps seem bossy and tedious it takes less than a few minutes to complete them. My girls crowd the gate to their run anticipating that once I'm done filling the pan I'll let them out for a while.
This is one way to help your ladies beat the heat - my girls needed some time to get used to the pan. Last summer when they were younger it took them a while to be willing to investigate it. I would recommend starting one like it between April and May the first year so when they need it, they aren't afraid of it.
I adore my girls! Northern Utah is a state of extremes - we have over 100 degrees heat in the summer and well below freezing temps in the winter. Breed wise, I choose cold hardy breeds. The breeds that are great in the heat don't normally compensate well to the cold. Cold hardy breeds are much better at dealing with both cold and heat - however chickens have a much harder time in the heat then in the cold.
Making sure they have access to plenty of clean water, feeding early in the morning and/or again later in the evening are simple but first steps to keeping them cool.