I have a 2013 XJ, I left my car outside in the driveway and it rained. When I went to move car in garage, I notice water pooled on the front passenger side floor. I touched it he trim

that goes alone the side of the windshield and it was damp. The seats, headliner, and armrest were all dry. How can I tell where the water is coming from?

 

step 1: don't live in a river

 

Sunroof drain most likely. But I couldn't give you any more info on how to access or clean it. We're having the same issue on my wife's Infiniti G37.

 

I wonder if that old Doobie Brothers song is playing in the car.

 

In my experience i suspect that the front right sunroof drain is plugged up. I used an old network cat 5 or better cable with the end cut off and fished it down the drain hole that is in the front corner of the sunroof "housing" and pushed it down till the drain was unclogged. You have to run the cable under the right corner of the sunroof popup air shield to get to the drain tube.

 

Yup - I just went through this with My S type -The first sunny day in a month in Seattle and I look out and see moisture on the inside of all my windows. I found the compartment behind the passenger seat FULL of water after the snowy winter . first off - get it in the garage and start drying it out or it will smell like mold. If you can pull the seat then do it. I already had my back seat out for a fuel pump repair so I just peeled up the carpet in the back and pulled the drain plug out. Then I stuffed dry newspaper under the carpet every day (in a 75 f garage mind you) to soak up as much water from the pad as I could. I really didnt want to pull out my front seat as the water was only in the back due to the car being on a slope. The pad is like a sponge though it really soaks up the water. You can use a wet vac if you have access to one but get as much water out of the car as possible. Buy a bucket of Dri-Z-Air too . That will take any excess moisture from the air inside the car. I also stuck a heater in mine for a few days. Just don't burn the car up
Once you get past that open the sunroof and take a cup of water and dump it carefully between the track and the roof body in each corner. You should see water dripping from the fender area behind each wheel well. Like XJsss said yours is probably plugged in the front passenger corner. Cat 5 cable,Tie wire or sometimes if you have a rubber fuel line and compressed air you can blow out the drain tube. Mine was full of pine needles
Good luck