California Car Covers and Carcoon. Both are very pricey. A buddy has a Carcoon and swears by it. He lives in an area that has 3 seasons which can be just less than extreme at times. But his car comes out looking like it did when it went in.
Like the other respondent, if you don't get much rain, leave the car uncovered. The wind will blow it all over and wear on the paint.
Cover dash, package tray and seats with towels to prevent sun damage. Put a shield in the windshield.