Wet carpet on driver's side front. No rain.?

I first noticed this the other day. Plastic-backed floor mat was wet and underneath carpet very wet. At first I thought maybe it was just rain coming in so I dried the mat and let the carpet dry then I replaced the mat. This morning I found both the carpet and (obviously) the underside of the mat wet again. It's a 1996 Civic DX with 160K. No rain and normal driving through no wet areas. Thanks in advance for thoughts.