I vote with these guys. Water, water and more water. When it's humid and nasty out, I will drink 60 to 80 ounces before I leave the house so I am well hydrated before I start. We have two coolers on each nine and I empty a 20 ounce water between each cooler and the clubhouse. Then refill at the clubhouse making the turn. The last time I went out it was really miserable and we just played 9 holes. But the above usually works well for me as long as we aren't waiting on taking our shots. Even staying hydrated though, 110* Heat Indexes are miserable to play in for me.