Wet Carpet in a Double Cab?

I have a 2001 double cab and last night while I was taking out the floor mats and putting new ones in I found the carpet in the backseat passenger side floor was wet.

It was more like damp than wet honestly. I let it dry out over night but it's still somewhat damp still and you can clearly see in this picture this brown mark. That's where it's most damp. Any suggestions to fix it or find the issue? It rained like two days ago. I haven't used the AC at all.

 

The seal around the door of mine leaks, doesn't let that much water in but could be your issue.

 

Maybe. I checked under the truck and didn't see any obvious holes or rusting. The weird part is that it's dry alongside the door and only wet in that corner by the cup holder and hump.

 

Weird. Put some newspaper down and keep an eye on it, might be able to tell where it's coming from. I remember hearing about people having similar problems and I'm pretty sure it was the weather-stripping.

 

Check the center storage area at the very bottom.
There are two bolts that have a threaded nut on the end of the transmission tunnel that are exposed to the elements.

Also check the door sills, meaning the plate.

 

back window or side glass gasket leak is my bet. if its wet in the back seat but dry by the door, unless you park on a steep hill, then it has to be something from the roof or the rear glass so if the headliner is dry they check for rust holes around the back window gaskets.

and shop vac that carpet until its dry or you will have mold and mushrooms growing back there in no time