Why fog forms on the windshield & how to keep it clear in heavy rainfall


Posted by: Ikeokwu Chidozie

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It is important to learn why fog forms on the windshield in heavy rainfall; then it will be easy to keeping it clear while driving. Read this to learn more.

Driving during a heavy downpour or even being a passenger in such situation should have allowed you experience the windshield becoming blurry and eventually covered with a layer of moisture. This layer of moist is how fog forms on the windshield, and makes it almost impossible for the driver to see the road clearly.

In this article, Naijauto will help you to explain why this happens as well as show you tips how to keep it clear during this rainy season.

1. Why does fog form?

We need to know what causes fog on the windshield in heavy rains because it leaves the driver and passengers in possible danger of an accident if it is not cleared out. A basic understanding of the situation can help us in the real challenge of a fogged windshield.

Windshield fog comes up as a result of the different temperatures and the moisture from air which is known as humidity. The windshield becomes cold from the contact with cooler air outside, while the air inside the car is warm from passenger breath. We have to consider that there will always be air trapped while the car doors are closed, the humidity levels of the different air results to fog forming on the windshield.


The differences in temperature inside & outside the car cause fog

Fog gathers on a rainy day when the warm air in your car meets your chill windshield; the moist or humid air becomes cooler to form the fog. The people in the vehicle are warm while the weather continues to drop in temperature outside the vehicle. This increases the rate of fog forming on the windshield as the air meets with the cold glass.

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2. How to defog the windshield in heavy rainfall

To prevent fogging, we need to make the temperature of the air inside which meets the glass surface to be cold or at least be close to the temperature outside. This can be called defogging the windshield, and we will see ways to achieve this in the vehicle while driving.

Follow these maintenance step to allow proper defogging;

  • The intake vents positioned outside at the base of the windshield has to be clear and free of dirts. These vents are supposed to allow fresh air from outside to get into the vehicle when it is in motion.
  • Cleaning the windshield from outside is easy, but it is necessary to clean the inside. Doing this will help fight against stubborn fog which condenses from the inside. Dirt particles that do not get cleaned will hold condensed moist when the situation for fog formation occurs; this is a slight explanation to why a dirty window will fog up faster and thicker than the rate of fogging on clean windows.

Steps to defog the windshield:

The usual approach which many drivers use is to turn on the air conditioning system (AC) to cool inside the vehicle to be close to the outside temperature. This will keep the windshield quite clear, but the individuals in the vehicle may need to be warm because of the cold weather. It is always better to apply the following;

1. Using the AC, set it to heating and select flow mode over windshield ; this will keep the windshield warm to balance with the air inside the cabin of the vehicle.


Modern car owners will find this function very familiar

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2. If your AC is disconnected, you can wind down your windows a little, so that outside air will enter and to reduce balance the air temperatures and reduce how fog forms on the windshield. The only disadvantage of this approach is that splashes of rainwater will get into the cabin.

3. You could also simply use fan only to blow air from outside into car through the AC vents.

4. Apply shaving cream to your windshield. To do this, you should use the type of shaving cream that foams up when you press it out of the can or bottle. Spray a small amount of cream onto a soft cotton cloth and spread it over your entire windshield; then use a clean, dry rag to wipe it off. This should create a moisture barrier on your windshield, preventing fog build up.

Defogging the windshield is all about regulating the temperature and humidity inside the vehicle correctly. The bigger the difference between the inside air and the windshield temperatures; if the relative humidity is low, then fog forms on the windshield.

Remember to always keep your vehicle clean whenever you have to set out with it, especially during the rainy seasons. Do not just rely on the rain water to wash surface stains away. The windshield of your car is completely important to safety; this is not just for the vehicle appearance, but also to allow the driver to observe the road ahead at every point in time.

>>> Check Naijauto for more car maintenance tips & safe driving advice!

Ikeokwu Chidozie

Ikeokwu Chidozie


Chidozie is an innovative content writer with an academic degree in Mechanical Engineering. He combines his experience in transportation and logistics with creative writing to provide his audience with credible articles on automobiles. Always visit naijauto.com and be guaranteed of expert vehicle reviews, tips, advices and news from this excellent writer.

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