It’s no surprise when ice forms on the outside of your windshield in winter. But seeing it form on the inside? That’s a little more unexpected. (Not to mention frustrating and confusing.)

The main culprit is moisture trapped inside your car. When temperatures drop overnight, this moisture condenses on the glass and freezes, leaving a thin but stubborn layer of ice that makes morning commutes even more of a hassle.

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This excess moisture can come from several sources. Wet boots, snow-covered jackets, and used umbrellas can all introduce humidity into the cabin. Even something as outwardly harmless as driving with wet hair in the winter can unknowingly add moisture that might contribute to ice buildup later. Leaky seals, blocked air vents, or a clogged cabin air filter can also make matters worse by trapping damp air inside.

Parking habits could also be part of the problem. If you frequently park your car in a garage or enclosed space with poor airflow, humidity levels stay high, increasing the chances of interior ice. Without proper ventilation, all that moisture lingers – and when the temperature drops enough, it freezes into an annoying, hazy frost on the glass.

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The best way to deal with interior windshield ice is to prevent it from forming in the first place. Begin by reducing the amount of moisture inside your vehicle. For starters, rid yourself of any excess snow or rain before getting into the cabin. You can also use rubber floor mats to trap water and then shake them dry when you get out of the car. Try to avoid leaving damp items like gym bags, water bottles, or wet umbrellas in the car overnight, as well.

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If your vehicle has a recirculation setting on the climate control system, avoid using it in winter — it traps moisture rather than allowing fresh, drier air to enter. You should also check your car’s weather stripping and seals to make sure they’re intact, as even the smallest leaks can let in moisture. Another trick: run your car’s defroster on a low heat setting for a few minutes before shutting off the engine to help dry out the air inside. While you’re at it, there’s nothing wrong with placing moisture absorbers (such as silica gel packets or a container of baking soda) under the seats to soak up even more excess humidity.

Even with the best prevention methods, you may still wake up to ice on the inside of your windshield from time to time. If that happens, don’t panic: there are quick and effective ways to get rid of it.

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To begin with, try to resist the urge to scrape the inside of the glass with a credit card or metal tool. Not only is it awkward and messy, but you also risk scratching the windshield, making your visibility even worse. Instead, start by turning on the car and letting the defroster run on a low or medium setting. (Avoid blasting hot air immediately, as sudden temperature changes can stress the glass and possibly even cause windshield chips or cracks.)

If you need a faster solution, a microfiber cloth can help absorb condensation during the melting process. Gently wipe the ice as it starts to thaw. This will help clear up the windshield without streaking. Another effective trick is using a solution of water and rubbing alcohol. Mix one part alcohol with two parts water in a spray bottle and lightly mist the icy area. Since alcohol has a lower freezing point than water, it helps break down the ice quickly. A few sprays while you defrost the rear windshield — yes, that’s what those lines are for – should clear the glass in no time.

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