Should You Use Hot or Cold Air to Defog in Summer?

[VonReid]

Both warm air and cold air can be used to defog a car. The differences and precautions between using cold air and warm air for defogging are as follows: Differences between the two: Using warm air to blow the windshield is more effective than using cold air because it essentially dries the water vapor, eliminating concerns about fogging up again. However, warm air defogging is slower than cold air defogging, and the fog may initially worsen when first turned on, requiring a few minutes of patience. If you want to quickly remove fog from the windshield, use cold air. Precautions for warm air defogging: In winter, using warm air for defogging is more comfortable. Although warm air takes longer to defog than cold air, it prevents the windshield from fogging up again. When the driver turns on warm air for defogging, the fog on the windshield may initially increase—don’t panic. After a short wait, the warm air will dry the fog.

[JackFitz]

In summer, when fogging occurs inside the car, I see many beginners struggling over whether to turn on the hot or cold air. Actually, turning on the cold air AC is the correct solution! Turning on the hot air increases the humidity and heat inside the car, making the fog even worse, especially on stuffy days after rain. The cold air can dehumidify and reduce noise, and with the fan blowing on the windshield, the fog clears in seconds. With decades of driving experience, I often encounter this on humid roads. I immediately press the defog button or turn on the AC, and the effect is excellent. Remember, safety comes first—don’t accelerate when visibility is blurry. If your car has an automatic air conditioning feature, it’s even more convenient. Also, don’t neglect regular maintenance, such as changing the air filter periodically to avoid system blockages. This little trick can make your journey more comfortable and worry-free.

[McCharlotte]

The principle of summer defogging lies in temperature difference and humidity control – hot outside air condenses into fog when it meets cold glass. Turning on the AC removes moisture through the refrigeration system, quickly clearing fog; while turning on the heater can raise the temperature to absorb more moisture, it initially increases condensation, making the fog worse instead of better. As a tech enthusiast, I've tested different car models and found the air conditioning mode to be the most effective: press the AUTO button to set the temperature, or manually turn on the AC and external circulation. Some high-end cars even have integrated defogging sensors for automatic adjustment. Don’t forget to check your car’s AC performance—the cleanliness of the filter affects defogging speed, and preventive maintenance can save a lot of trouble.

[EverlyAnn]

When I was a new driver, my car windows fogged up in summer. I tried using hot air, but it made the fog worse. Later, I learned that I must turn on the AC with cold air—it reduces humidity and removes moisture. The manual operation is simple: turn the air conditioning switch to the defogging position, increase the fan speed, and it will be done in a few minutes. Using hot air wastes time and increases fuel consumption. This season has more rain and is prone to fogging, so develop a good habit of slightly opening the windows for ventilation before getting in the car. Preventing fogging at the source is easier than dealing with it later. If your car has no major issues, mastering this trick will improve daily convenience.