I live where it can get seriously hot (90 - 105) and stay there. When that happens, sensible people stay indoors, if they can.

If not, then conduct this mental exercise: think about the interior of your body. It is 98 degrees in there, and the humidity is 100%. Now think about the air. It is also 98 degrees, and the humidity is high. You are one with nature. Don't worry about it.