My 2000 did the same thing. You need to look at the "A" pillers on the front doors. Pull your trim and door seal off and you will see it. The welds that the factory did sometimes don't seal. When it rains or you was your car the water gets in passed the seams. Go to a dealer, ask for the repair kit for the piller seams and the leak will stop. It take about two hours for everything to dry before you put your trim back on. Good luck.

 

Update....it is still happening. I haven't figured out where it is coming from yet, but I do know that rain is causing it and not air conditioning...which I was pretty sure it wasn't before anyhow. So give me some ideas of how to locate this problem. I don't see anything leaking in by the window, although when i went in my car yesterday there was a puddle on the side by the door, but I can't tell where it is coming from.

 

Have you tried pulling up the carpet and sprinkling foot powder? It can be a little tedious but it works. I would check first in the trunk around the tail lights, and if its not there than pull the carpet out of the front and sprinkle the foot powder. After that, take it to the car was or soak it good with a hose, you will see where it is wet right away.