What to Do When Car Windows Fog Up on Rainy Days?
2 Answers
Press the defogging button, turn on the air conditioning cooling (A/C) switch, set the temperature to the lowest, and turn on the external circulation to defog. Fogged car windows can be cleared using either cold or warm air, but warm air defogs slower than cold air. The most effective method is to use cold air, which blows dry, cold air directly onto the glass, preventing water vapor from condensing on the surface and achieving defogging. The method for defogging with warm air is the same as with cold air, but it's important to note that warm air should not be used for defogging on rainy days, as it can initially worsen the fogging. Always use external circulation when defogging car windows. The reason car windows fog up: There is a temperature difference between the inside and outside of the car. If the temperatures inside and outside are different, the surface with the lower temperature will have a lower saturation vapor pressure than the surrounding environment, causing water vapor to accumulate on the glass surface in the form of tiny droplets, creating fog.
The most annoying thing about driving in the rain is foggy windows! When I first started driving, I used to wipe them blindly with a towel. Later, a mechanic taught me a few tricks. Turning on the AC and blowing cold air directly at the windshield is the fastest way—the fog clears in seconds. Avoid using hot air when the car interior is already warm. If the side windows fog up, crack them open slightly to allow airflow, which prevents condensation. Don’t forget to turn on the rear defroster—the heating wires make clearing fog super convenient. The key is not to breathe directly onto the glass. When there are many passengers, use the external air circulation more often. If the outside of the windshield fogs up, it’s usually due to worn wiper blades—just park and replace the rubber strips. Developing good habits is better than anything else. Running the AC for a while to dehumidify before driving is much safer than scrambling to fix foggy windows later.
