You need to get a car cover that is rated for outdoors. You should look for the following:
-Rated for Outdoor Use
-Soft Fabric Inside, so it doesn't scratch the paint.
I use the following, but I do store the car indoors. It’s rated for outdoors use though. It has a pretty soft inside, and I take caution not to get the inside dirty. I always wax the car before putting it on.
CanadianTire - Simoniz Car Cover, 17½-19 ft. $99.99
Or, you can try the premium ones.
CanadianTire - Simoniz Pure Premium Car Cover, 17½-19-ft. $179.99