A note on where humidity or moisture comes from:  the bees themselves.
Remember we have several pound of bees respiring away all winter in
that hive.  If we had a 3-4 pound cat enclosed in a small box we would
certainly expect to have have a build-up of moisture from the water
released through the cat exhaling.  Differential temperatures can cause
water vapor to condense but the temperature differential doesn't create
the moisture--just makes it visible to our eyes.