I live in Charleston, South Carolina. Our summers are brutally hot, temps in the high 90's - 100's and the humidity is about 1000%. I'm not kidding. There is a saying in Charleston that "it's so humid the clothes rot right off your back!!"
You will not see me outside without my "wet washcloth". I wear it around my neck, and use it a lot to wipe the sweat from my face.
You will also see me riding in shorts, because the alternative is to not ride at all.
What do you do to keep cool?? I could use more ideas.