Wet concrete

Guess it's the right forum to ask.
We have MIL with 3 garages on the slab. MIL is on the 2nd floor.
One of the garages is my "shop" so to speak, with tools, workbench and large mower.
We had several thunderstorms today and for some reason I walked into that shop.
Immediately noticed that floor - concrete - looked wet. I'll post pic tomorrow, it's almost 9pm here. But entire floor looks like one large wet stain and then bunch of wet dots. About quarter size. They disappear towards the center wall (two car garage behind it) and wet stain is on the outside wall side.
No puddles. Simply either solid wet or dotted wet concrete. Now, I have wet soil behind that wall that dries out only after quite a few hot sunny days and it's been pouring here for about 6 months. Today it was bad downpour several times.
We have none of this issue in the main house garage.
I noticed no wet drywall or anything dripping.
Any ideas? Can water sip up into concrete from saturated ground? I have no idea if any drainage was done around foundation.

 

It will depend on whether a moisture barrier was used below the concrete when it was poured. No barrier, and yes, it will migrate to the surface. I think what you have is simple humidity settling on the floor. Remember the concrete is much colder than the air above it and with all the rain and warmer temperatures, humidity will certainly be a problem.

 

I think so too. Reason being some wet spots are not connected. If it drains /drips from somewhere they'd be all streaked together. Yet it's a spot here stain there.
Good question about moisture barrier. Who knowd. I'll monitor it.
I dug dirt away from the outside wall and saw no signs of any tar or bitumen or even black paper.

 

Were the doors open? If the concrete is cool and you open a door warm moist air will condense and make the concrete wet even if there is no leak.

 

I am on staycation so door is open most the time. garage door.
I took pics but of course, my phone is updating itself so... A bit later. But it looks much drier today than yesterday.

 

It's dry. Not that it was not raining, it rained on and off all day long. But it's dry. Maybe simple clearing foundation from dirt did the trick.
I'll keep monitoring it.