how cold is it in the caves?

44F year round.

Pretty cool. Light jacket or sweater would be ok. I think they said 45*

You need a light jacket

Low 50s. Definitely need a jacket. Lots of stairs and inclines, so the activity warms you up.

Mid 40s definitely bring an extra layer

Pretty darn cold. Even if it's hot outside, you should wear long pants and long sleeves.