It should be completely dry if the cover is up against it. But even with 40 degrees, the sun and wind will dry it out soon enough.

Also, you many want to check with the manufacturer to see what they suggest for winter protection. Also, it might not be a bad idea to leave some sort of airgap between the cover and the table surface, such as with a couple pieces of wood or pvc, but again, just check with the mfr.

I'm guessing if it was made for outdoors that they've tested it for that environment and would warn you otherwise. Of course, you can't count of that.

My mom has a plastic tablecloth for her dining room table and the underlining is a thick flannel type material. It's used under a regular tablecloth, but its purpose is so you can set hot casseroles, etc. on it without damaging wood. Wonder if something like that would work in conjunction with normal patio table cover? Just to help isulate it? I agree you may want to leave an air gap.

Just throwing that out there....