Are they open on rainy day?

Yes they are always open it's the same temp in the cave always.

Yes

They are open 7 days a week the cave stays at 53 degrees they have a pump inside to pump out the water so rainy days dont matter !

They are. The entrance is right off the Swatara creek so in heavy rain the caverns have flooded in the past, but under normal circumstances, they are open. The stairs leading from the visitors center to the entrance of the cave are covered, but the rest of the area is exposed.

I guess so

Yes, we went on a rainy day. Unless the adjacent river is flooding over, they're usually open to tours.

Yep!