Watch the episode of Hey Arnold where there is a giant heat wave. Then watch the part where the kids are trying to tip over the Jolly Olly mans truck. You can easily see that the armpits of the kids and the Jolly Olly man are very, very sweaty (and brown). Then right after it starts raining, the Jolly Olly man says he's getting out of there, and it is very easy to see that his armpits aren't sweaty anymore. He certainly dries easily...