Trying to explain to Kelly last night why sweat cools the body (or not, depending on humidity), I mentioned swamp coolers. I just found a site that has a rather good explanation, so here it is.
Update: To date I've received two requests for more information about swamp coolers from interested readers. To be clear, I don't have a swamp cooler and never have. The website I've pointed to is a good starting point for more information, or you can of course try Google.Good luck!