What Causes Fogging on the Front Windshield in Summer?
2 Answers
Because air conditioning is generally used when driving in summer, the temperature outside the car is lower than that inside, causing the water vapor inside the car to form many tiny water droplets. The surface of the front windshield is not perfectly smooth (it has many small pits), so these small water droplets adhere to the front windshield, resulting in fogging. The following methods can be used to remove the fog: 1. Open windows for convection: If the fog is not heavy, you can open a gap in the side windows to allow air convection inside the car. When the temperature inside the car approaches that outside, the fog will dissipate. However, this method is only suitable for low-speed driving. 2. Adjust the air vent direction: Choose a blowing direction that does not target the front windshield to eliminate the fog.
I've been driving for several years, and fogging on the front windshield in summer is really common, especially for those of us who frequently drive long distances. It's mainly because the outside temperature is high and the humidity is high, and when you turn on the AC, the interior cools down quickly, causing the glass surface temperature to drop suddenly. When warm, moist air hits the cold glass, it's like water droplets forming on the outside of a cold glass—water vapor condenses and causes fogging. This happens even faster after rain or in coastal areas where the air is more humid. Personally, when I encounter this, I always stay calm, turn up the AC fan speed, switch to defog mode, and direct the airflow at the glass—it dries out after a while. I’ve also noticed that the cleanliness of the windows makes a big difference; if there’s grease or dust on the surface, fog tends to gather more easily, so regular glass cleaning is important. For long-term prevention, you can adjust the AC temperature to avoid excessive cooling and large temperature differences, making driving safer and more comfortable. With clear visibility, it’s also less frustrating.
