Why Are My Windows Streaky After It Rains?

If your windows look worse after rain than before it, you’re not imagining it — in San Clemente, this is usually a sign of what was already on the glass before the rain fell, not a problem with the rain itself.

What’s Actually Causing the Streaks

Rain doesn’t stain glass on its own. What it does is run down through whatever’s already sitting on the surface — salt film from the marine layer, dust from a recent Santa Ana event, or mineral residue left behind by a previous cleaning with standard tap water. As it evaporates, it leaves that residue in streaks rather than washing it away cleanly.

This is especially common on homes that get a DIY clean with a hose and squeegee: San Clemente’s water runs hard (roughly 295 ppm), so the water itself leaves mineral spotting behind — and the next rain just makes that spotting visible in streak patterns.

How to Actually Stop It

• Clean with deionized water, not standard tap water, so nothing mineral-rich is left behind to streak later
• Have frames, sills, and tracks wiped along with the glass — debris sitting in a track channel runs back onto “clean” glass the next time it rains
• Match your cleaning interval to your exposure — see our Service Area page for typical intervals by neighborhood

For more on why this happens specifically in San Clemente, see our pages on salt air and hard water.