Yes, they do if you find the correct one and place it according to the instructions. If your place there is a lot of snow or wind flow, these covers will act as a safeguard to your windshield. You don't have to scrape snow and ice off the windshield every time, which is a great way to avoid scratching the glass.  Aside from that, a cover also protects your windshield from dirt and debris that could cause damage. Be sure to check the description before you buy to make sure it protects against your main concern, whether it's UV rays or frost.