When I was a kid, we didn't have air conditioning and when it was 110 degrees or so outside, my mum would drape wet towels over an open window - because the air flowing over the wet towel creates evaporation which cools the air. You gotta keep wetting the towel as it dries though. Else put a wet towel in front of a fan for the same effect. And if you don't have any breeze, you need a fan. I do this in the car sometimes too cause my aircon isn't working well.
Also when I have heat rash, just draping a wet washcloth over the area helps. Again the evaporation cools the skin.
I heard somewhere that wet cloths on the pulse points (wrist, forehead...) work best because there is increased blood flow there. Don't know if this is true or not.
BTW this evaporative cooling idea was how the settlers in Australia used to keep food cool. Drape wet fabric around a wire mesh 'cupboard'.