Streaks happen for a few reasons: wrong squeegee technique, dirty or worn squeegee rubber, skipping the frame and sill (which drips dirty water back onto the glass), or using too much soap that leaves a film when it dries.
The real cause most homeowners don't know about: some crews are on a tight route and prioritize speed over quality. They'll spray and wipe with no real technique and move on to the next house.
Ready for streak-free windows?
Book Window CleaningIn South Florida, hard water mineral deposits and salt film also make streaks worse. They require a proper scrub before squeegeeing — not just a rinse.
The fix: make sure whoever cleans your windows uses clean rubber, works top-to-bottom, wipes the frames first, and does a dry pass at the end. A quality window cleaning job should leave glass that looks optically invisible. If it doesn't, the job wasn't finished.