Heat domes are doing more than baking American cities this summer — they're changing the outcome of baseball games in ways most fans never see coming. Hot air is thinner than cool air, meaning baseballs travel farther on the exact same hit, turning routine pop flies into home runs. Studies show that more than 500 extra home runs since 2010 are directly tied to warming temperatures and with more heat on the way before the MLB season ends, the summer heat may have more to do with the box score than anyone realizes.