What to Do When the Outside of the Windshield Fogs Up?

[SawyerMarie]

When the outside of the windshield fogs up, here are several solutions: 1. Open the windows for air circulation. If the fogging is mild, slightly open both side windows to allow air exchange inside and outside the car. The fog will dissipate when the interior temperature approaches the outside temperature. However, this method is only suitable when the car is moving at low speeds. 2. Lower the fan speed and turn on the external air circulation, then set the airflow to fully blow onto the windshield. This method is slower in defogging and is only suitable for mild fogging. 3. Mix a defogging solution with dish soap and water in a ratio of about 1:10, then apply it to the glass with a cloth. This not only defogs quickly but is also cost-effective. If dish soap is unavailable, windshield washer fluid can also help. 4. If the fog is heavy and neither opening windows nor using wipers works, adjust the air conditioning to warm air, increase the temperature, and direct all airflow to the windshield. The fog will disappear quickly with very noticeable results.

[SanAlice]

I remember one time after it rained, I drove out and suddenly the windshield fogged up outside, blurring my vision instantly, which was quite dangerous. I quickly used the windshield wipers to swipe a few times, and the fog reduced a bit, but it didn’t last. Then I turned on the car’s air conditioning, set it to dehumidify mode (that’s the setting where the fan icon points to the windshield), adjusted the temperature to cool air—avoid using hot air because it can make the outside more humid. It cleared up quickly. The principle is that the air conditioning’s dehumidification function reduces the humidity of the external air, preventing condensation. I’ve made it a habit to switch the air circulation from recirculation to fresh air before parking, allowing the car to ventilate and disperse moisture. Also, regularly clean the windshield with glass cleaner to reduce oil buildup that attracts water droplets. If fogging happens frequently, check if the air filter is clogged—if it’s old, just replace it with a new one. These methods are simple, safe, and practical.

[DeDavid]

I find that when the windshield fogs up on the outside, the most effective approach is a three-step process: First, immediately turn on the wipers to quickly sweep away the moisture. Second, activate the car's air conditioning, switch to dehumidification mode, and set the airflow direction to blow directly onto the windshield area. Third, adjust the fan speed to medium to allow the cool air to circulate and dehumidify. Avoid using hot air, as high temperatures can make the exterior more humid. If your car has a heated mirror function, turn it on to assist with defogging. Fogging usually occurs due to rain or high humidity causing a temperature difference between the inside and outside of the glass, so air conditioning dehumidification is key—it effectively balances humidity and prevents recurrence. If it happens while driving, slow down and pull over to ensure safety before addressing it. I also recommend keeping a bottle of anti-fog spray in the car—one application lasts about a week. Regularly check the ventilation system while driving to ensure it’s functioning properly. These small tips make driving safer and free from fog-related distractions.

[VonLeo]

Windshield fogging on the outside mostly occurs in humid weather, such as rainy, snowy, or foggy days. At this time, the glass temperature is lower than the dew point, causing moisture to condense into water droplets on the exterior. My experience is: immediately activate the air conditioning's dehumidification mode, directing cool air toward the windshield, which can quickly remove the fog layer. Avoid incorrect operations, such as only turning on the heater—this will make things worse. If there's no air conditioning, lowering the windows for ventilation also works. In daily use, I keep the glass clean and free of stains to reduce moisture adhesion. Additionally, during regular car washes, I specifically clean the windshield surface and use hydrophobic coating products to allow water droplets to slide off without accumulating fog. Simply put, timely dehumidification ensures safety.