I had this problem and the seal that runs above the rocker panel had come loose. As you're driving in a rainstorm water gets in at the bottom of the door. If you haven't done it already, check under the drivers seat. I had a 1/4 inch of water pooled around the DME. Luckily it didn't short out.

I'm with Tom. Make sure it is water. And, make sure it is not the A/C. The leak may be from inside the vehicle.

It could also be that the trunk seal isn't secured. I had to silicone my trunk seal into the "gutter" because water was filling the gutter area closest to the windsheild and overflowing into the trunk area.

Hi,

I had this weird leak into my driver's footwell. Finally discovered it was from a faulty windscreen washer seal !! The water tracked all the way into the car from there....go figure.:p