The best day to clean windows is when the weather conditions are favorable for the task. Interior windows don’t matter as much, but for exterior windows, ideally, we would prefer a day that is dry and not too windy. It’s also beneficial to clean windows on a cloudy day or when there is no direct sunlight. This helps to prevent the cleaning solution from drying too quickly, allowing for easier removal of dirt and grime, and reducing the likelihood of water spots. Ultimately, the goal is to have optimal conditions that facilitate efficient cleaning and allow for a streak-free finish.