Twist the hinge rail screws a quarter turn each, counterclockwise, using a flat screwdriver. This loosens the tension in the hinges to make the door easier to open. The hinge rail runs vertically along the hinge side of the door.
Spray a silicone spray lubricant into the door's latch mechanism. Wipe off any excess lubricant with a rag. Try to open the door.
Find the latch rail on the latch side of the storm door, which is the side with the latch and door handle opposite the hinge side. Do this if you still cannot open the storm door after loosening the hinge rail screws and lubricating the latch mechanism.
Extract the five screws from the latch rail, using a screwdriver, and remove the latch rail from the side jamb. This frees the storm door to open.