Open your front door to allow access to your storm door. Choose a fair-weathered day without excessive wind, rain or cold. Not only will this keep your house interior from being exposed to bad weather, but extreme temperatures and conditions may affect the process as well.
Clean the storm door surface thoroughly. Use a soft, clean cloth and either an all-purpose cleaner or a specialty cleaner designed for the storm door material. Glass cleaner and newspaper works well on glass, for instance. While technically you only have to clean the area immediately under where you will place the magnet, it's a good time to make the whole door look sparkling clean.
Dry the entire storm door with another soft, clean cloth, or use newspaper if glass cleaner was applied. Allow the storm door to air dry an additional 20 to 30 minutes to ensure all possible moisture has evaporated.
Determine the exact location where you want the magnet situated. If you have something specifically that you intend to hang from the magnet, hold it in place to estimate the location you desire. Alternatively, use a tape measure to situate the magnet location precisely, measuring over and either up or down from the door's edges to calculate.
Dab up enough rubbing alcohol to moisten a cotton ball. Swab the entire spot where you want to place your magnet to ensure all oils are removed. Dot the location with the tip of a marker to pinpoint the location later.
Clean all the magnet's surfaces with rubbing alcohol and a fresh cotton ball to remove any dirt or oils. Dry the magnet thoroughly and allow it to sit out for 15 to 20 minutes to ensure all moisture has evaporated.
Grasp the magnet and flip it over so that the side that will adhere to the storm door is facing up. Abrade this surface, using either a small piece of sandpaper or a nail file. Scuff it enough that you feel and see the roughness. The irregular surface helps glue to bond since it creates a greater surface area.
Brush the magnet off with a soft, clean cloth. Use rubbing alcohol and allow drying time if any grittiness remains when you touch the underneath surface of the magnet.
Spread a thin layer of glue on the bottom surface of the magnet. Choose a polycarbonate glue or epoxy or a specialized adhesive recommended for the storm door surface. Consult the product label to determine if the glue will work well with your storm door.
Press the magnet to your storm door in the marked location. Hold it in place as directed by the glue's instructions.
Dip a cotton swab into nail polish remover and run it around the outside edge of the magnet if any glue oozed out when the magnet was pressed against the door. The acetone in the nail polish remover should lift fresh glue. Use straight acetone, alternatively.