Short answer
Usually not. Rainwater itself is low in minerals and runs off clean glass with little trace. The spots people blame on rain usually come from dirt already on the glass, frames, or screens — or from mud and sprinklers splashing up. That's why clean windows stay looking good through a storm and dirty ones look worse.
Why dirty glass looks worse after rain
Rain mixes with the dust and pollen already sitting on a window and leaves it behind as it dries. On clean glass there's nothing to mix with, so the water mostly sheds away. Dirty screens and frames above the glass can also drip grime down onto it.
What we do about it
We wash screens and wipe frames and sills as part of every window cleaning, so there's less dirt waiting to run back onto the glass. Exterior glass is rinsed with purified water, which leaves no soap film to attract new grime.
If you're worried about timing
We don't need to reschedule for light rain in most cases. If a heavy storm or freezing temperatures are coming, we'll talk with you and move the appointment if it makes sense.
Rather have a pro handle it?
Pro Solutions does window cleaning across Boise and the Treasure Valley. Quotes are free, itemized, and usually texted the same day.