water under floor mat passenger side only

[lbuggie]

I noticed under the floor mat on the passenger side that I had water under the mat. It was a lot of water, and the thick black insulation pad is saturated. I removed the floor mat, and removed the pad to dry it up. I know it's not coolant. The water is crystal clear. The car is under a cotton cover all winter long, and it was dry before storage I check these things out before storage. I have not washed it yet this spring. The defroster/heater was run a few days this winter when I drove it for a few short distance runs. Any ideas where the water might be coming from?

Thanks !!!!!