Chickens don't sweat like humans do to cool down. Much like dogs, they pant to help stay cool.
When they are very hot, you will also see them holding their wings out slightly from their bodies and ruffling their feathers to help the heat escape.
Be sure they have plenty of shade and fresh, cool water when it is hot outside. Water is extremely important! A lack of water, even for a few hours, can throw them off laying, put them at risk for heat stroke, and make it difficult for them to manage their body temperatures.
But you can also give them another way to help stay cool by dedicating just a moment at night, and a few extra minutes in the morning.
How refreshing it is to have an icy glass of cold water when it's hot outside? Very. And it's refreshing for your chickens, too! Remember, if it is 95 degrees outside, the water in their waterer may also be 95 degrees. But you can give your chickens cool water for most of the day by putting a block of ice in their waterer in the morning. Simply freeze water in a plastic storage container, empty sherbet tub or even a water bottle overnight, and then plunk it into their waterer in the morning. Ice cubes will work of course, too, but they will melt more quickly, so the water won't stay cool for as long. Large blocks will help keep their water cool all day, and can help your chickens stay cool in the worst of the summer heat! You can also try feeding them some refrigerated or even frozen treats, such as melon (which also has a lot of water to help keep them hydrated) corn, peas, grapes and so on. Try freezing treats in blocks of ice to be given to your flock the next day.
Make sure you offer these frozen treat blocks outside, as you don't want all that ice melting into water in the coop, and soaking the bedding. We recommend using metal chafing dishes as they won't crack in the freezer and make a mess. The metal also makes it easy to remove the ice block, and they are easy to clean. But other alternatives are reusing paper milk or cream containers. When everything is frozen, you can simply peel the paper off the ice.