There's a product in Home Depot that you can buy to clean your windows from the outside. You'd remove your screens, and then attach this container of cleaner to your garden hose and spray it onto the windows. It's supposed to dry without streaks much like windshield washer fluid (and that could be what they make it with for all I know).
You'll find it in the cleaning aisle and it is specifically for house windows. Usually, it's with a similar product for cleaning clapboard siding.
