On Sunday, May 19, 2019 at 5:46:08 PM UTC-4, JBI wrote:
Due to job cuts, this past Winter I ran minimal heat in the house, just
enough to keep temps above freezing so the water pipes wouldn't freeze.
Now I don't live in the house often and there is some neglect, like I
haven't mopped the kitchen floors in a year and they are linoleum.
Today I noticed something odd. It is the first really warmer day and I
opened up the doors and windows in an effort to heat up the house
interior, which was around 70 F when I opened up this morning. This
afternoon, I noticed some moisture on the kitchen floor. At first I
thought it was just in one area, but the entire floor seems to be what I
could describe as sweating. I can run my finger even over remote
sections, which of course bring a layer of dust onto the finger, but
also it's moist at the same time.

Bottom line is that I've never noticed this before. Is this something
that can just happen, or what's going on? I suppose if I gave it a good
mopping and removed the dust layer, there wouldn't be enough dirt for
the moisture in the air to cling to... just a guess.

The floor was cold and you let in warmer moist air, nothing unusual.