Questions:

1. In what part of the world do you live? Has it been raining a lot?

2. Are you running the air conditioner a lot? Even if you have the
heat lever all the way over, running the AC will still condense
moisture from the outside air as it is drawn into the passenger
compartment.

3. Do you smell coolant?

If yiu live in some place where it has been raining, I would suspect
water coming in from outside.

2. If you are running the AC a lot, it could be that the AC drain is
stopped up. If that's the case it is easy to unstop (with a piece of
wire) if you can get under the car.

3. If you smell coolant, then it is likely a leak in the heater core.

Arguing against 2 and 3 are the facts that leaks form those sources
are most likely on the passenger side.

Hope this helps

Elliot Richmond
Freelance Science Writer and Editor

Jim,

I had a similar problem with my 97 Civic.  It turned out to be a rubber
body plug that was missing.  The plug was on the side panel about half
way up.  I sealed the hole and have had no problems with water getting
in.  You may want to check that.  You might have to remove the plastic
kick panels to check.

Mike

It could be just the melted snow off your footwear. I have that problem on
occasion.

It can also as bad seal around the windshield.

My 91 civic has the same problem but worse. I still haven't
figured it out, but this was my idea. Perhaps a bit boring, but
remove all the paneling inside before a heavy rain, then sit in
the car while it's raining. Check to see where the water is coming
in while it's happening. I've already detected several leaks. One
is coming from the upper seal in the windshield. I'm guessing it
came loose after I punched the windshield. Maybe it's just old as
hell. It's amazing that the major crack in the glass doesn't leak
but the seal does.

Also on the roof of the car there are two channels that look like
they're filled with a bondo-like material. Water is seaping in
through there. I'm planning on tearing this up and going bondo
crazy. Thirdly there is water coming in one of the screws on the
sun roof. Water is also trickling in from the dashboard below the
glovebox. I have no idea how, but it does.

I once drove my CRX through a minor flood and discovered that much
water can actually come UP through the floor in several different
locations. It was shooting up like I had 20 squirtguns on the
floor pointed up. I have my carpet up and I'm planning on giving
it even more of the bondo fix. With the door panels off, I've also
noticed water coming down the window channel and into the door. I
forsee a future problem with the bottom of the door rusting out.

Finally, after removing the back seat on my sedan, I noticed water
coming dripping into the trunk. After removing the carpet I
discovered I was lucky to even have a trunk compartment with all
that rust. I took care of that with a grinder with a wire wheel,
rust remover chemical and some good old primer.