Car cover for winter?

[Senor_Taylor]

So, the roof on my Miata leaks a little during really bad rain. Not enough to mess up anything, but on such a special interior such as mine, I'm worried about any moisture. It's A-Okay in the barn here at home, but I'm worried about sitting outside at JMU and the eventual snow if I don't manage to get the car stored in the barn for winter (Which I'm not sure I'd want anyway with the barn cats and other animals in there.)

What are my options? Will a car cover destroy my paint that quickly if I'm just using it for 2 semesters? Can I just cover it if I know it's going to rain? Maybe a shower curtain or something over the roof?

Edit: To clarify, the roof doesn't leak, the seals on the windows do, which I may be able to remedy. I could possibly pick up a Miata fitted cover for cheap and I could wash it well before putting it on.