Drink lots of water, literally. If this doesn't work you're not drinking enough. Drinking massive amounts of water does cool your body and takes away that sticky, hot, misery, of being borderline dehydrated.
Very few people drink enough water and they are always the ones bitching about the heat.
Stop taking wimpy-boy sips and gulp that water down by the gallon like a man. People like me, and Netsua, will laugh at your discomfort until you do.
Haha.