The inside temperature of the window is below the dewpoint temperature of the air in the home. The solution is warm-up the window temperature or reduce the dewpoint of the air in the home. I suggest increasing the introduction of outside air into the home for a couple reasons. The most important is to remove indoor polutants and second is to remove the excess moisture. To test the idea, operate bath fans or kitchen hood continuously for a couple days or open a window a little. Suggest a good exhaust or make-up air system.