Why is the velodrome so hot?

Excuse me, but I was wondering if you could help me understand why the velodrome is so incredibly hot? Is it due to the design of the building, the materials used, or perhaps the high-intensity activities that take place within? I'm particularly interested in knowing if there are any measures in place to mitigate the heat and ensure the comfort of athletes and spectators alike. It seems like a challenging environment, so I'm curious about the strategies employed to make it more tolerable.