[heisenzombie]

<man walks into sauna room> Ooh, it's a bit hot in here! I better throw some water on these rocks to cool them down.

Joking aside, I actually don't know how dry it is in the underground, and therefore whether adding water for evaporative cooling would work. I would have assumed it was quite humid, but maybe not?

[Cthulhu_]

It would be if they tried cooling it with water, for sure; evaporative cooling would only work if there's enough airflow, else they'd just get 100% humidity so it would be both hot and humid.