water coming from under dash

When it rains I get a small amount of water on my passenger floor mat.
Under further investigation (removed glove box and plastic piece that covers air blower?) I found water sitting in depression of plastic piece that is below motor for blower. I bring in plastic piece to dry out as it has some foam on it I guess for sound proofing. The next day after work I start my car (it has rained lightly all day) turn on fan for defrost and a lot of water falls from under dash. So now I guess the water is coming in from where fan gets out side air supply. Any suggestions

Thanks so much

Check the drain hole, it is probably clogged. Usually located on the passenger side of the firewall. You can open it by putting a piece of wire through the hole.