Part of the preflight that pilots have to do is calculate how much runway is needed for takeoff given the planes loading and current conditions. If the plane d

Part of the preflight that pilots have to do is calculate how much runway is needed for takeoff given the planes loading and current conditions. If the plane doesn't include data for the current temp, they can't run their calculations and fly. It's not that the plane itself can't fly in the heat, but they often aren't tested at very high temps due to lack of need.