I had the opportunity to catch a game at the Arizona Diamondbacks' stadium a few years ago. The temperature in Phoenix was about 98 at game time on the last weekend of May. I walked into the stadium to a cool blast of air. I thought that they had a closed roof when it got so hot. Instead, they had duct work that was probably ten feet in diameter blowing cold air toward the field, with the roof open. It was a massive waste of energy, but it was good for watching a game.