What Causes Windshield Fogging in Summer?

[LaJoshua]

Fogging on the inside of the windshield in summer is caused by the temperature difference between the interior and exterior. When the window temperature falls below the dew point, the air's moisture content is insufficient to form water droplets, resulting in tiny water particles that condense on the window surface, creating the fogging phenomenon. Solutions for Windshield Fogging: Using Detergents: Dish soap 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 dish soap, mix water and soap in a 9:1 ratio, spray it on fog-prone windows during rainy weather, let it dry, and then gently wipe it off with a soft tissue to prevent fogging. External Air Circulation: If rain is frequent and opening windows isn't practical, use the external air circulation mode for defogging. Proper vent settings should direct air to both the windshield and footwell or just the windshield. For vehicles with automatic climate control, the compressor may not activate at lower temperatures, so allowing interior and exterior air to circulate can help disperse fog. Anti-Fog Sprays: There are specialized anti-fog sprays available for car windows. These products absorb moisture from the glass surface, forming a thin film that prevents fogging. After application, wipe the window dry with a cloth to maintain clear visibility, with long-lasting effects. Window Adjustment: After driving outdoors, park and open the windows to let warm air in. Within a few minutes, the temperature difference will decrease, and the fog will dissipate. If parking isn't an option, use windshield wipers to clear fog from the front and rear windows. For side windows, rolling them up and down can help remove fog by scraping it off with the window seals.

[DeAubrey]

I think the main reason for fogging on the front windshield in summer is the significant temperature difference between the inside and outside of the car. The outside is as hot as a steamer, and when the air conditioning is turned up high, the glass gets cold, causing moist air to condense on it and form fog. I often encounter this issue when driving on rainy or humid days, with water droplets being particularly noticeable when humidity is high. If not careful, it can obstruct vision and be quite dangerous. I usually turn on the air conditioning's dehumidification mode in advance or direct cold air toward the windshield; if necessary, I open the window slightly to allow air circulation. For prevention, regularly cleaning the glass to reduce oil film and maintaining the air conditioning system are crucial, as they can lower the chances of fogging. After adopting these small habits, the fogging problem has become much less severe.

[GiaAnn]

From a scientific perspective, summer fogging is a physical condensation phenomenon. When warm and humid external air comes into contact with the cold glass surface, the air temperature drops below the dew point, causing water vapor to condense into droplets. I've observed that this situation is prone to occur when the air conditioning is set too cold or when humidity is excessively high, especially after heavy rain. Preventive measures include keeping the glass temperature close to room temperature, such as not setting the air conditioning too low; ventilating briefly before driving, or using the defogging function to directly disperse the fog. Applying these principles has significantly improved my driving experience.

[LeKira]

Preventing fogging starts with daily maintenance. I make sure to keep the air conditioning filter clean to avoid internal moisture buildup; the glass is regularly treated with specialized cleaners to reduce dirt attracting moisture. Preheating the air conditioning before driving is essential, avoiding sudden blasts of cold air. Moisture management is key—check window seals during rain. Simple maintenance can prevent problems, ensuring better visibility and safety.