Why Does the Outside of the Windshield Fog Up When Driving in the Rain?

[LaAshlyn]

Rainy day driving causes the outside of the windshield to fog up due to significant temperature differences between the interior and exterior environments, or large humidity variations. If your vehicle is equipped with manual air conditioning, turn on the front window defogging mode, set the fan speed to maximum, turn on the A/C switch, and then adjust the temperature to the lowest setting to dry the fog on the windshield. If your vehicle has automatic air conditioning, simply pressing the one-touch defrost button will usually eliminate the fog quickly. If the ambient temperature is too cold for using the air conditioner's cold air, you can also turn on the heater, set the airflow to maximum, and activate the front window defogging mode. The fog should disappear within a few minutes. Most rear windshields come with electric heating, so you can directly turn on the rear windshield heating and mirror heating functions to quickly remove fog and prevent it from forming again.