Avoid Streaking Windows, Do Not Wash Them in the Sun
It is helpful to clean the windows inside and out from time to time, but the ugly streaks can make it look like you never washed them at all. You can reduce the chance of streaking by not cleaning windows in the hot sun.
Spraying soap or detergent on the outside of your windows can help get rid of the build-up of dirt, but Ashley Poskin of Apartment Therapy suggests saving window cleaners in case the windows are in the shade and cool. The sun can heat the glass, causing streaks. For best results, you can use a squeegee and overlap the strokes, but if you don’t have one, a little newspaper will work too.
How to clean a window | Apartment therapy