Why Does the Windshield Fog Up in Summer?
2 Answers
Fogging on the inside of the front windshield in summer is caused by the temperature difference between the inside and outside of the car. When the window temperature is lower than the dew point, the moisture content in the air is insufficient to form water droplets, resulting in tiny water particles that condense on the window surface, leading to windshield fogging. Solutions for window fogging: Using detergents: Dishwashing liquid or soap can be used to prevent fogging on car windows. Soften the soap by soaking it in water, then apply it evenly on the glass surface. Once the soap dries, wipe it off with a tissue or newspaper. For dishwashing liquid, mix water and detergent in a 9:1 ratio and spray it on fog-prone windows during rainy days. After drying, gently wipe with a soft tissue to prevent fogging. External circulation defogging: If it rains frequently and opening windows is not suitable, turn on external circulation to defog. Properly adjust the vents to blow air toward the front windshield and footwell or just the windshield. For cars with automatic air conditioning, the compressor may not activate at lower temperatures. In such cases, allow air exchange between the inside and outside of the car to disperse moisture and achieve defogging. Anti-fog spray: There are specialized anti-fog sprays available in the market for car windows. These sprays absorb moisture on the glass surface, forming a water film that prevents fogging. They prevent moisture from adhering to the glass, and wiping the windows with a cloth afterward keeps them clear for a long time. Rolling down windows: After driving outside, park and open the windows to let warm air in. Within two to three minutes, the temperature difference decreases, and the fog will disappear automatically. If stopping is inconvenient, use windshield wipers to remove fog from the front and rear windshields. For side windows, roll them up and down to scrape off fog using the window seals.
Last summer, I remember turning up the AC in my car and the windshield fogged up so badly I could barely see the road. The reason is pretty straightforward: it's scorching hot outside, but the cold air from the AC chills the glass, causing moisture from passengers' breath to condense on it. The fix is simple—direct the AC vents toward the windshield and crank up the fan to dry it out. If your car has a defog button, just press it. Avoid using recirculation mode too much; switching to fresh air mode helps vent out humidity more effectively. I also keep anti-fog wipes handy for quick cleaning. Regularly cleaning the windshield prevents oil buildup that worsens fogging, and cracking the window slightly when there are passengers helps too—prevention is key. Since adopting these habits, summer driving has been much smoother, safer, and hassle-free.
