Pros clean windows on cloudy days on purpose

Ever cleaned a window in full sun and watched it dry streaky before you even finished? That's not your technique — it's physics. Direct sunlight heats the glass and flash-dries the cleaning solution before it can be squeegeed off, leaving behind the mineral residue that shows up as streaks and spots.

Professionals plan around it: working the shaded side of the home, cleaning early or late, and — most importantly — using deionized, purified water that dries with zero residue no matter how hot it is. That's why a pro clean stays clear instead of clouding over by the afternoon.