If you live in the northern states and don't have a garage, then you're probably quite familiar with the headaches caused by windshield frost. Basically, this hard-to-scrape-off layer is caused by airborne water droplets settling on the windshield (i.e., dew) then freezing. As such, the key to prevention lies in keeping the moisture from settling on the surface in the first place with a simple homemade cover.
Apply a small bead of silicon glue to the flat side of a 1/2-inch round ceramic magnet. Inexpensive ceramic magnets can be found at your local Radio Shack electronics store or online.
Press the glued side against the inside of the windshield in the far upper left corner. Hold it in place until it sets (usually four minutes) then let it dry for eight hours. Perform this procedure for the remaining three magnets.
Measure the height and width of your windshield from the outside, then add 2 inches to the width measurement.
Use the scissors to cut the vinyl tarp to fit the measurements (i.e., width + 2 inches by height).
Lay the cut tarp onto the windshield, then place the four unglued magnets on top of it so that the glued magnets underneath hold them in place.
Outline each of the top magnets with a marker then remove them, along with the tarp.
Glue each of the magnets to their respective marker outline on the tarp. Note: make sure that each magnet is glued to the right place; otherwise, they won't be attracted to the windshield-mounted magnet underneath.
Let the glue dry for eight hours.
Remove all ice and snow from the windshield with an ice scraper.
Fill a spray bottle with isopropyl alcohol then spray the entire front of the windshield with a mist of the solution.
Take out the magnetic vinyl tarp and lay it on the windshield, lining up each of the corner magnet pairs.
Smooth out the surface of the tarp with your hand once or twice.
