Somehow, water is getting into the trunk of the car. It's not coming from rain because even after the car has been rained on for quite some time, the trunk is dry. It's when I'm driving in the rain that the trunk gets wet so it must be coming in from the bottom somewhere. I had some boxes in the trunk and when I went to get them, they were all damp and getting soft. None of them had an actual wet spot that I could see but they were certainly damp. The cloth on the floor of the trunk is damp too but even there I couldn't pinpoint where the water was coming from. I'm going to have to do something like maybe remove everything and line the whole trunk with newspaper and take it for a spin in the rain and then check for the wet spots. Whenever I do get around to actually doing that, I'll post the results here.