Why Does Car Glass Fog Up in Summer?

[MacKhloe]

In summer, car windows fog up due to the low temperature setting of the air conditioning inside the car, which creates a significant temperature difference. Additionally, the direction of the air conditioning airflow may not be properly adjusted, such as when it blows directly onto the front windshield or the side windows. The cold air from the AC lowers the temperature of the glass, and when this cold glass comes into contact with the warmer outside air, especially in high humidity conditions, it easily forms a layer of condensation on the outside. Here are some solutions to prevent window fogging: 1. Open windows for air circulation: Crack open the side windows slightly to allow air to flow between the inside and outside of the car. When the interior temperature matches the exterior temperature, the fog will dissipate. 2. Use the AC defogging function: Press the A/C button (which stands for air conditioning cooling), lower the temperature, turn on the window defogging function, and set the fan speed to maximum. This helps evaporate moisture on the glass surface and quickly cools the window to remove fog. 3. Use anti-fog spray: Anti-fog spray works by applying a protective film on the windshield to prevent condensation.

[JulietAnn]

I'm a young driver who drives every day, and every summer when I turn on the AC, the car windows tend to fog up. That time during a heavy downpour, I could barely see the road! The reason is actually quite simple: in summer, the outside is hot and humid, while the car's AC is set to a chilly temperature. When warm air hits the cold glass, it condenses into water droplets, like a layer of fog smeared on the window. This is especially worse on cloudy or rainy/snowy days when the air is even more humid. My car often does this, and I almost missed a turn because of it. Now I've learned my lesson—after turning on the AC, don't blow it directly at your face. Switch to recirculation mode or use the defog button, or even wipe the windows with a cloth. This way, visibility clears up faster, and driving feels much safer.

[Quentin]

As a seasoned driver with twenty years of experience, I'm no stranger to foggy car windows in summer. It's mainly caused by temperature differences and humidity: high outdoor heat and humidity, combined with the cooling effect of the car's air conditioning, causes moisture from breath or rainwater to condense on the cold glass, forming fog. I've encountered this several times, even when parked in the shade, which can be dangerous on highways. The solution isn't complicated—usually, directing cold air from the AC toward the windshield or briefly opening the windows to circulate air will reduce humidity and clear the fog. Preventive maintenance is also important, such as regularly checking seals for leaks and turning on the AC for dehumidification in advance during rainy or snowy weather.

[KendraFitz]

As someone who prioritizes driving safety, I find summer window fogging extremely annoying. It obstructs visibility, making driving feel like navigating blind and significantly increasing risks. The root cause is the large temperature difference between cold and hot air—when the car's air conditioning meets external heat, moisture condenses on the glass. This often happens during rainy seasons or humid weather, requiring constant vigilance while driving. My advice is to address fogging immediately—don't wait for an accident. The simplest solutions are pressing the car's defog button or directing cold air at the windows. If you're in a hurry, briefly opening the windows for ventilation can quickly dissipate the fog.