Interesting question there, when it's hot as in early archery season. I go the opposite of cold wet weather all cotton. I know it run's against the grain of most guy's thinking, but when it's hot you sweat a lot, a tee shirt get's wet with sweat, any breeze hit's the moisture on your tee it cools the tee which in turn cools your skin. Same thing that happens when you wear cotton in cold weather. Wet cotton dry's slow and cools your body down and in cold weather you sure don't want that hence the old saying in cold wet weather cotton kills.