How old are they, etc? What are you keeping them in/ around? Make sure if they're young and under a heat source you give them plenty of space to get away from the heat source, and LOTS Of free choice water.
If they're older and in a coop/ etc, same deal-- make sure they can get to a cool spot, plenty of water, and sometimes I've heard of people filling soda bottles and freezing them and setting them in the coop on hot days so they can get some relief from the heat that way. Make sure there's ventilation and fresh air.
I *think* you can spray them with a water bottle to help relieve some of the heat, but not sure-- best to wait and see if someone else with more experience comes along.
Chickens do pant to get rid of heat, so they just might need to cool down a bit that way.
Good luck!