If you let it go long enough, you can enjoy the pool sloshing from side to side on turns, and freezing into a skating rink in the winter. That and the black mold. Ah, memories! Probably one or more bad seals or perhaps this one time a window was cracked open ever so slightly and the wind was just right. It's best to get it throughly dried out and check for moisture hiding in any depressions under the seats, etc.

OP, even if it's not the sun roof this time, it's a good idea to get the drains cleaned when you have regular tune ups. Damage from a sun roof leak is a total mess. I usually ask for the extra service just because I've read horror stories.

Update from OP: we poked a wire hanger down the drain pipes from the sunroof but they didn’t seem clogged. We poured some water down to make sure they drained out, which they did. At this point, we’re thinking it could be a seal problem with the door or drivers side window or sunroof... It’s just that the absence of water anywhere else, including rain splatter and dried water marks is the head scratcher. Hoping it was just a fluke thing. But we will know after the next big storm. Thanks again everyone for your great suggestions!

Thanks everyone. We are going to check things out based on these tips. Had no idea about the sunroof drains!

Anonymous wrote:Door seal leak

This

Sunroof drain tube clogged with debris. In my SUV this was fixed by poking at it with a coat hanger. It’s on the underside of the body around the driver footwell

Check seals around windshield.

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Always the sun roof

Most probable answer. There are draining channels built into the sunroof that lead to drain lines that run to the bottom of the car. One of these is likely blocked. I’d bet that it’s the drain that runs down the frame along the windshield. This is usually a simple fix for a DIY type or the dealer.

Yes. This. Had the same problem and it was driving me crazy. Took the car in and the auto technician knew immediately what the problem was. I had no idea there were drainage tubes that could get clogged.

I had a passat with this same issue. The sunroof was the culprit, draining issue

Door seal leak

Anonymous wrote:

Anonymous wrote:Always the sun roof

Most probable answer. There are draining channels built into the sunroof that lead to drain lines that run to the bottom of the car. One of these is likely blocked. I’d bet that it’s the drain that runs down the frame along the windshield. This is usually a simple fix for a DIY type or the dealer.

Yes. This. Had the same problem and it was driving me crazy. Took the car in and the auto technician knew immediately what the problem was. I had no idea there were drainage tubes that could get clogged.

Anonymous wrote:Always the sun roof

Most probable answer. There are draining channels built into the sunroof that lead to drain lines that run to the bottom of the car. One of these is likely blocked. I’d bet that it’s the drain that runs down the frame along the windshield. This is usually a simple fix for a DIY type or the dealer.

Always the sun roof

Get a hose and hose down the car like rain would and see what happens. Maybe doors, maybe the sunroof after all, read about this tons of leaks.
Google also rain water in the car and see what you get, all problems already happened somewhere so just find those who have some experience with them.

rust hole in floorboard?

This is a weird one. We had heavy rains where I live last night and this morning when I got into my car there was a puddle of rainwater on my driver side floormat. The windows and sunroof were closed and the doors were completely closed/locked. The weird thing is there is no water or dried water stains anywhere else on the car — not on the side window, front window, dashboard, seats etc. We are stumped. If water came down through the hood and down through the steering column I presume we would have water on both floor mats which we don’t. Any ideas? Off to shop vac...