Why Does Frost Form on the Outside of the Windshield in Summer?
2 Answers
Because the temperature outside the glass is higher than inside the car, the hot air outside the window meets the cold air inside, condensing into mist and adhering to the outer surface of the window. Hazards: Frost forming on the outside of the windshield in summer can obstruct the driver's view while driving, which is detrimental to road safety. Treatment Methods: Start the vehicle's engine to warm up the car. Turn on the interior fan and set it to the hot air mode, directing the airflow toward the windshield. Once the external frost has melted, use the wipers or a cloth to wipe it away and remove the frost. If you're in a hurry to leave, you can use a professional cleaner for a quick fix, but be careful not to scratch the glass.
I've encountered windshield frost on the outside several times in summer, mainly due to temperature differences and humidity. Although summer days are hot, nighttime temperatures can drop sharply, especially with radiative cooling bringing the glass surface temperature below the dew point, causing moisture in the air to condense into frost. This often occurs in high-humidity environments, such as when the car is parked near lawns or riversides, where dew evaporating from the ground contacts the cold glass and forms frost spots. Another factor is parking location—shady areas under trees or low-lying spots with poor air circulation tend to accumulate humidity, making the problem worse. For simple prevention, I recommend choosing dry concrete surfaces over grass when parking, or investing in a good windshield cover to avoid the hassle of scraping frost in the morning.
