Ever considered a dripping wet cotton T shirt? Makes a great swamp cooler, and everyone has cotton Ts around. This is one place where cotton is actually a good idea. This cooler might not work for those of you back east where high humidity goes along with high heat and evaporative coolers are ineffective.
Oops, I'd better clarify my geography! To most residents of the Pacific NW, even Colorado is "back east"! However, I grew up in Wyoming, so to me "east" doesn't start until central Nebraska.
That's also more or less where summer heat starts to correlate with high humidity.
Because my dog is even more sensitive to heat than I am, my hot weather workouts or hikes start at the crack of dawn.
It actually got up to 82* here yesterday and I thought I was going to die! Until this past weekend, highs have been nearly all in the upper 50's or very low 60's, with a few days in the low 70's.