Why do windshields fog up in the rain?
Windshield fogging is caused by condensation on the inner surface of the windshield, and not the outside. So wiping down the outside is useless. Condensation happens on the windshield because of the high humidity inside the vehicle, and the fogging is because of the temperature outside is colder than inside your vehicle. Think of how moisture that gathers on the outside of your drink, this is the same scenario.
How to properly get rid of fog on the windshield?
The fastest way to take care of foggy windows is to turn your A/C up and make the inside of your vehicle colder than the outside temperature.
To clear away any fog, wipe away any moisture with a lint-free cloth before turning up your A/C also and putting your A/C on the setting where it blows directly onto the windshield.
What if the fog won’t disappear?
When you cannot get the fog on your windshield to disappear, you most likely have oil mixed with moisture causing that hard-to-remove smidge on your windshield.
Oil can come from something like the cleaning product you used to wipe the surfaces or even the type of air fresheners you have in your car. Some air fresheners when evaporating, can get oil particles on your windshield, especially in hot conditions. If you have oil on your windshield you can clean it off by using just a little bit of rubbing alcohol or soda on a soft cloth and rubbing it across the oiled area.
How to prevent your windshield from fogging up.
The best way to keep your windshield from fogging up is to keep the class clean. Any dirt or oil particles like magnets for moisture. For long lasting effects you can use anti-fog coating products. Make sure your windshield is clean and dry before applying any anti-fogging products.
Check your weatherstripping
The weather stripping on your doors and windows can deteriorate, which is leaves a door open for moisture to seep though the side of the window. If you find any damp areas on the inside of your vehicle this is a immediate sign your weather stripping needs replacement.