The area I live in had a heat wave for the past two days, with temperatures near 90 and the high humidity that characterizes unpleasant East Coast summer days.
The first day I just suffered through it (I was too lazy to put my window air conditioning unit in). But the second day I remembered something I'd once read about.
I filled a metal water bottle with ice water, and alternated holding it against each of my carotid arteries, and in the crook of each arm. Within four minutes I was no longer sweating, and this kept me completely cool for as long as the ice lasted, which was about an hour.
Try it, it works.