Prevent Your Windshield from Fogging in the Rain

The metro has been experiencing heavy rainfall recently. How did you fare when your windshield fogged up? Low temperatures combined with damp weather make the perfect recipe to throw a little more misery to an already gloomy day. If you’ve wiped the windshield clean and fiddled with your car's AC controls to no avail, it helps to understand why windshields fog up so you can take the most appropriate course of actions for your malady.

Why do windshields fog up in the rain?

Windshield fogging is caused by condensation on the inner surface of the windshield, and NOT the outside, so it’s completely useless for you to go out in the rain and wipe or squeegee the glass until your fingers go numb. Condensation on the windshield happens because of the high humidity inside the cabin, and the fogging is because the temperature outside is colder than what you have inside your car. This is similar to the moisture that accumulates on the side of your drinking glass whenever you drink a cold beverage. The more humid air comes in contact with the cold windshield glass, thereby releasing moisture and leaving condensation or fog on the glass.

How to get rid of fog on the windshield

Because warm air loves moisture, the fastest way to take care of foggy windows is to turn your AC up and make your cabin colder than the outside environment. To clear away the fog faster, wipe your windshield surface with a clean, dry, and preferably lint-free cloth before turning up your AC. Likewise, most cars have an AC setting that blows cold air onto the windshield directly through the cowl. Take the time to learn this AC function, as this is another way to speed up the disappearance of the moisture that has collected on your windshield.

What if the fog still won’t disappear?

It's most likely that moisture has mixed with oil, causing that hard-to-remove smudge on your windshield. The oil can come from the cleaning product that you use to wipe cabin surfaces or the type of air freshener you have in your car, which can evaporate onto your windshield during extremely hot temperatures. Oil can also come from the dirt particles that find their way onto your windshield. A dab of rubbing alcohol or soda on a soft cloth is a quick and easy way to get rid of stubborn windshield oil.

How to prevent your windshield from fogging up

The best way to prevent windshield fogging is to keep the glass clean. Dirt and oil particles are like moisture magnets, so keep them away from your windshield as best you can by cleaning the glass regularly with a microfiber cloth and water. For long-lasting effect, you can use anti-fog coating products to keep the moisture at bay. Make sure your windshield is clean and dry before applying such a product.

Make sure to check your weather-stripping

The weatherstripping on your doors and windows is made of rubber, which can deteriorate over time. When this happens, moisture can seep through and enter your cabin. If you find damp spots on your upholstery after parking or driving in heavy rain, or if you can hear the rain in your cabin even when the windows are shut, this may indicate that some--if not all--of your weatherstripping seals need to be replaced.

Updated as of July 13, 2020 by Cherryl Anne Cruz