You don't even need to be nearby the ocean to have that problem Rocky. I suppose it's more likely just the extreme temperatures we get up North with the quick changes.
It's been said that Pennsylvania roads suffer the most potholes because of all the freezing and then thawing we have here. New York State has less thawing due the it being further North. It's typical here to have frozen roads at night and into the morning hours which then thaw in the afternoon only to freeze again when the sun goes down.
In an enclosed area with a cement slab (and the metal of the bikes), the slab as you said holds the cold while the air temperature is higher. Not only do we get surface rust, but also white oxidation (which turns to pits) on any aluminum parts.
I always insulate my tires from the cement floor with cardboard too.
Luckily, I have heat where I store my bikes in Winter which removes the humidity.