It gets very hot and humid here in Florida too and these are some of the things we do to help our chickens feel more comfortable:
* Water, lots of fresh water and extra waterers so they don't have to go far to find it
* Frozen water bottles put inside their waterers helps keep the drinking water cool
* Large shallow plastic pan with 2-3" of water in it is nice, they love to stand in it (kid's swimming pools can work too if the sides aren't too tall)
* Cool treats like grapes, melon, frozen vegetables
* Hosing down the dirt so they can stand some place cooler
* Natural and artificial shade. If you don't have many trees, rig up something like a tarp covered frame they can sit under.
* Lots of ventilation in their coop and a fan set up high to move the air but not blow directly on the chickens
* Replace glass windows and solid doors with hardware cloth openings to help with ventilation
It can take some extra work to do all that but it's worth it to make them feel better and avoid heat-related deaths.
Good luck to you!