storm door 
noun chiefly North American
An additional outer door for protection in bad weather or winter.In any case, never add a glass storm door if the door gets more than a few hours of direct sun each day....
- Add an attractive storm door to protect the entry door and keep heat inside in the winter, and bugs out in the summer.
- The outer door was propped open, the storm door the only one keeping the bugs from entering the house.