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Winter Road Trip Safety: How to Defog Your Windshield Fast

October 28, 2019

A car is driving down a highway at night in the rain.

Dear Golden State Auto Glass & Tinting,
I hate when my windshield fogs up. It makes driving difficult and can be a real nuisance, especially when I’ve to get somewhere on time. Is there a way to defog my windshield as quickly as possible?
Yours sincerely,
Can’t See Through My Windshield

Hi Can’t See Through My Windshield,
Presuming you’re concerned about winter fogging, there is indeed a quick way to defog your windshield—and it’s totally based on science.
But before we get into its details, let’s first understand why your windshield gets fogged up in winter anyway.

A car is parked on the side of a snow covered road.

We have warm air and cold air; the air inside your car is warmer, while the air outside your car is colder.
Since your car’s windshield is exposed to the outside colder air, it is also comparatively colder than the air inside your car.
Warm air can hold more moisture than cold air. So, when the warmer air inside your car comes in contact with the colder windshield of your car, its temperature drops and it loses water, which you see in the form of fog (or condensation) on your car’s windshield.

A blurry picture of a car driving down a road in the rain.

Now that you know what causes fog on your windshield in winter, let’s take a look at how you can quickly defog it.
To defog your windshield, you must either:
a) Decrease the moisture content of the air present inside your car; or
b) Increase the temperature of the air inside your car so that it can soak up moisture from the windshield
You can use both these strategies as well to accomplish faster defogging.
To decrease the moisture content of the air present inside your car, turn your car’s AC on; this will help absorb moisture from the air. Furthermore, open your car’s windows to exchange the more humid air in your car with the dry air from outside.

A close up of a temp and push a/c button

To increase the temperature of the air inside your car, clock up your car’s heater to maximum settings. Let the heater run for a few minutes and watch the fog completely disappear from your windshield.
Hope that helps. Wish you a happy and safe winter season.
Golden State Auto Glass and Tinting is your trusted auto glass shop in San Jose, California. We provide quality windshield replacement, windshield chip repair San Jose, auto glass tinting, paint protection Bay Area and taillight services. Contact us today to schedule an appointment.