What Causes Fogging on the Outside of the Windshield in Rainy Weather?
3 Answers
Fogging on the outside of the front windshield during rainy days is caused by the temperature difference between the inside and outside of the vehicle. The temperature inside the cabin is higher than outside, leading to the condensation of moisture inside the cabin on the inner windshield, forming fog. Below is an introduction to the causes and solutions for windshield fogging: Causes of windshield fogging: The main reason for fogging inside the vehicle is the temperature difference. When the temperature inside the vehicle is higher than outside, the windows are prone to fogging. Additionally, high humidity inside the vehicle and the warm breath exhaled by passengers can cause condensation when it meets the cold glass, resulting in fogging. Best solution: The quickest and most effective method is to turn on the air conditioning's cold air. By activating the air conditioning's cooling function along with the external circulation, the fog on the glass should disappear in less than a minute. During autumn or winter, using the air conditioning's warm air to blow on the windshield is recommended.
As an experienced driver, I have frequently encountered the issue of fogging on the outside of the windshield during rainy days, primarily caused by condensation due to the temperature difference between the inside and outside of the car. The air humidity is very high on rainy days, and the outside air is warm, but the surface of the windshield becomes cold. This happens because when the car's air conditioning or cool air blows toward the inside of the glass, the internal heat conduction causes the glass surface to cool down. As a result, the warm, humid air condenses into droplets or a fog layer upon contact with the cold surface. Practical solutions to this issue include immediately turning on the windshield wipers to clear the fog or adjusting the direction of the air vents to avoid direct airflow onto the glass—preferably choosing an upward airflow direction. For preventive measures while driving, applying an anti-fog spray to the surface and developing good habits to check settings can significantly reduce unexpected risks and ensure driving safety, especially during nighttime rain when visibility is poor. Maintaining clear visibility is crucial, and I’ve learned from experience to address the issue promptly.
Windshield fogging on the outside is common in rainy weather, essentially caused by water vapor condensing when the glass temperature falls below the dew point. Primary triggers include the car's air conditioning blowing directly onto the interior of the glass, causing the exterior to cool, combined with high humidity from rain, leading to moisture in the air forming tiny water droplets. My first recommendation is to use the windshield wipers to clear the fog layer immediately, as this is the quickest way to restore visibility. If it happens repeatedly, adjust the air conditioning vents to direct airflow sideways or downward to avoid direct contact with the glass area. For prevention, regularly cleaning the glass surface and applying a soapy water solution can help reduce the issue, and maintaining the ventilation system is also crucial. For safety, avoid distractions while driving—prioritize maintaining clear visibility to effectively lower the risk of accidents, especially in severe weather conditions.
