Wear a pair of compression pants and Gerry Davis pants. The under garments actually feel cooler because they wick moisture and breathe well. They also eliminate the need for anti monkeybutt powder. I call tournamnets almost every weekend from late Feb/early March thru Oct/Nov. 9 is a slow weekend.
I do always wear a pair of under armour compression shorts but the best feeling in the world after the third or fourth game is to sit on the truck tailgate, wipe my face with some ammonia water and hike my pants up to feel a little breeze. I have found out that in the world of umpire clothing you can either get "moisture wicking" or "breathable", but rarely both. i'm at the point where i need more breathability.