Clean those screens before the winter weather sets in.
Clean screens with dusting attachment of a vacuum cleaner or brush with carpet scraps that have been nailed to a wooden blocks.
For a through job, dust the screens and brush with kerosene on both sides. Remove excess with soap and water.
Take hopelessly dirty window screens to a do-it yourself car wash. The high-pressure hose shoot streams of hot soapy water to clean off all dirt and grime.