Coal mines are usually at “the average yearly temperature” for a region, typically 55 to 59 degrees F.
Caves the same.

Coal cleaning plants are another matter.
140 degrees working on the furnaces that heat dry coal.
Sweating in Summer heat as you unload dry dusty coal from bottom dump rail hopper cars wearing N95 mask, hearing protection, gloves and steel toed boots.

But by far the worst is when winter rain followed by a sudden freezing snap causes wet coal in hopper cars to freeze.
You pry the doors of the hopper open, then have to swing pick axes and crow bars to break the coal loose, while sub freezing temp degree winds whip, and electric motor driven 15 ton “shakers vibrate the railcars causing 140 dB noise. You can not slow down because the longer the wet coal stays in the hopper cars the deeper the frozen layers of coal become.