Caulking and weather stripping around your doors and windows should be checked at least twice a year, once in the spring and once in the fall.  While you're cleaning up around the yard, have a look at your home's exterior for any weather - related wear and tear.  The finishes around your doors and windows should be checked for paint deterioration or rot, particularly the sills. Repairing the caulking and/or weather stripping is not a hard job, it just takes a little time and can be tedious if you have a lot to do. Work on one window or door at a time.  Don't get too far ahead of yourself.  Start by removing the old caulking or weather stripping.  Caulking can be removed by scraping it off with a scraper or a proper caulking remover tool (available at the hardware store).  Old weather stripping should also be removed including any residual glue. In both cases, try your best to have a clean, debris free surface.  Apply new window caulking to exterior window by taping off the edges leaving approximately 1/2 inch visible area (channel) to apply the caulking into.  This creates an even edge on both sides of the window surface and exterior wall surface.  Make sure to remove the tape before the caulking dries. Cracked caulking and deteriorated weather stripping can make a difference in cooling or heating your house. (It can also help keep the bugs out!) You can find caulking and weather stripping at Lowes, Home Depot or your local hardware store.