It seems like the trunk cover is always a little damp. I have one of the mini heavy duty rubber covers on top of that. Does anybody else have this issue?

 

@AngieG

Do you have any lights or devices that has wires running from the outside into the inside of your car? If not, the rubber seal around the hatchback maybe worn out.

 

Also check the antenna seal, I had to replace the base as it had weathered away and there was evidence of a small leak on the inside of the roof liner

 

Sunroof drain leak, main trunk gasket, or the seal around the antenna as the ones that leak.

 

After a long drive in heavy rain, there was water on the right hand side trunk for the first time. The reason was the trunk seal being just slightly loose at the top right corner of the hatch. It was still holding on tight to its frame support, just not pushed in all the way (maybe a couple or three millimeters off). Yet this allowed water to creep between the seal and the frame.