What Type of Air to Use for Defogging Car Windows in Winter Rainy Days?
2 Answers
When driving in winter rainy days, use cold air to defog the windows. Principle of Cold Air Defogging: The most common method to deal with fogged windshields while driving in the rain is to turn on the air conditioner and direct the airflow to the front windshield. The cold air quickly disperses the fog on the glass, providing fast and direct results. This happens because the cold air creates a "cold air film" on the glass surface, preventing carbon dioxide from condensing on the glass, thus achieving the defogging effect. Why Not Use Hot Air in Winter: Hot air can also defog, but if used to defog the front windshield on a rainy day, it can actually worsen the fogging. Right after turning on the hot air, the front windshield may immediately become like "frosted glass." Therefore, if you are driving and the windows fog up due to rain, you should not use hot air for defogging.
When my car windows fog up on rainy winter days, I immediately activate the defogging mode: typically by adjusting the AC to blow warm air onto the windshield while turning on the A/C dehumidification function. The warm air quickly evaporates the fog, while the A/C removes moisture from the car interior. If the car has a dedicated defog button, one press does the trick; if not, manually adjust the airflow and direction to the windshield icon position. Never open the windows—outside is wet from rain, and opening them will make the fog worse and more dangerous. Every time fog appears, I test the method when parked, safety first. If the fog is too thick while driving and affects visibility, slow down, pull over safely, and then handle it. Experience tells me that regular maintenance of the AC filter is crucial—if it's clogged, defogging becomes less effective, easily leading to blurred vision.
