Moisture under driver's carpet, how much is reasonable?

[nuttinnew]

Pulling the carpet up to put the locking key back in I noticed there was moisture present. I popped out the toolkit and the well is dry, likewise the passenger side. I've taken the driver's side out now and there's a degree of cold/dampness but no sign of a leak. The rear is dry also so I'm not thinking it's the rear vent, I have haven't checked the openSky drains yet though.
Is it likely moisture could be present after a wet winter? It hasn't much use before or after I've bought it, certainly not enough for the climate to do much dehumidifying so I'm wondering if it's soaked through from wet feet

 

[tfj]

This was the problem I experienced and found that the windscreen was leaking. A new screen was fitted last year following a crack and the leak was found by holding blotting paper on the inside of the screen when water was poured on the outside. I was surprised that this was the fault as there were no other signs.