I spent quite a but of time in a gold mine, (yes, an actual gold mine!), and one of the things I noticed right away is if you go more than 50 feet in or so, it’s ALWAYS the same.
Pretty much. There is no weather.
Here in Grand Rapids, gypsum used to be mined. That was played out long ago, but that temperature stability you mentioned has proved an asset for longterm storage of important documents and whatnot, for various businesses.