Why Is My Windshield Fogging up in the Summer? Easy Fixes

“Why is my windshield fogging up in the summer?” is a question that has crossed the minds of many campers as they try to figure out the cause. Interestingly, foggy car windows are not only a winter problem but can happen in the summer; thus, it shouldn’t be a surprise.

Windshield Fogging Up

In this article, we’ll look at the common reasons why this happens and how to defog windshield in summer humidity. We’ll also talk about how to prevent it and answer a few questions as well.

Why Is Your Car Windshield Fogging up in the Summer?

Your car windshield is fogging up in the summer because of reasons such as temperature variances, high humidity, condensation, surface tension, and heat.


Also, a malfunctioning air conditioner and other leaks in your vehicle can cause foggy windshields even in the heat of summer.

– High Humidity During the Summer Can Cause Fogging

Your windshield or windows are likely to fog up on days or in areas with high humidity, especially when you’re not the only one in the car. Humidity is when there’s a lot of moisture in the air, and this happens a lot in the summer since warmer air holds more moisture.

When the temperature begins to fall, especially during the evenings, the warmer air in the vehicle begins to cool. The process of cooling, called condensation, turns the air into moisture which rests on the inside of the windshield.

Also, the air outside can lose its heat as the temperature drops and turns into moisture. Since moisture is heavier than the air, it drops onto the surface of the windshield. This is why you’ll see fog on the windshield when you wake up in the morning.

– Surface Tension on the Windshield Encourages Fogging

Surface tension occurs when the liquid that has already settled on the surface of the windshield attracts more liquid. This is because the molecules of the water on the windshield attract and bond with the other molecules of water in the air.


As the surface tension increases, the droplets of water or moisture begin to spread across the windshield. Before you know it, the entire windshield is fogged up, blocking your view of the road ahead.

– When the External Temperature Is Different from the Internal

Another reason you’ll experience a window fog is when there is a variance between the temperature outside the car and the one within it. Usually, what happens is that the hot air holds a lot of moisture, which will condense when it comes into contact with cold air on the other side.

Windshield Causes Fogging

The condensation process forms tiny droplets of water on the coldest side of the windshield, causing it to become fogged. The temperature at which the fog normally forms is around 4.5 degrees Fahrenheit.

For instance, parking your car outside can cause a foggy windshield, with the fog forming either inside or outside the vehicle. If it’s colder outside than inside, the fog will form on the inside of the windshield. However, if the air inside is colder than the air outside, then fogging up will occur on the outside of the windshield.

– Turning on the Air-Recycle Button or the Airconditioner

Also, using the air-recycle button can produce more cold air inside the vehicle, which condenses when it comes into contact with warm air outside the windshield. There are two settings responsible for keeping the car cool on sunny days. One brings air from outside and cools it, while the other recycles the already-cooled air in the car. The latter cools the already cooled air by recycling it, thus saving energy and improving the efficiency of the air-conditioner.

The air recirculation button features an image of a car with a curved arrow, and using it keeps dust and pollen from entering the vehicle. This protects you from allergens and other irritants that could harm you. However, it can fog up the windows from the inside, which can be difficult to wipe away.

Using the airconditioning can also result in the same issue on both colder and warmer days. As explained earlier, if the air-conditioner is too high, it’ll condense the warmer air outside the vehicle. This will form tiny droplets of water on the windshield and can distort visibility when driving.

How To Fix the Fogging of a Car Windshield in the Summer?

To fix the fogging up of your car windshield in the summer, make use of the wipers on the windshield, turn off the air-conditioner, and use an anti-fog cleaner. You can also prevent fog from forming on your windshield by reducing sources of moisture and using shaving foam.

– Keep Your Windscreen and Windows Clean With the Wipers

One way to clean the fog on your car’s windshield is to use the windscreen wipers. Depending on the thickness and viability of the wipers, the fog may leave traces behind. When this happens, you can dispense washer fluid onto the windscreen and set the speed of the wipers to low. This should clear up the windscreen and give you better visibility.

– Turn Off the Aircondtioner or Use Heat Simultaneously

Another way to defog windows is to switch off the air conditioner, especially when it is the primary cause of the situation. Next is to roll down your windows and allow some fresh air setting to enter until the fog clears before putting them up again.

Fix the Fogging of a Car Windshield

You can repeat the process if you realize the fog forms up anytime you roll up the windows and turn on the A/C. However, this can be a laborious process; thus, you can rather turn on the heat button to counter the effects of the A/C.

For this to be successful, set both air-conditioning and heat to full power, with the heat being on the highest setting. The heat will cause air to evaporate while the A/C will dehumidify the air, thus canceling each other out. The temperature outside the windshield will be the same as the one inside, effectively getting rid of the fog. This trick is very useful in clearing the fog and improving visibility while riding.

– Clean the Windshield and Windows With an Anti-fog Cleaner

You can also clean both sides of the windshield with a cloth and then clean the inside of the windshield with an anti-fog cleaner. This method is also useful when the car windows fogging up inside winter season.

Take note that dirty windshields are more likely to get fogged up because tiny particles create better areas and conditions for condensation. Thus, they cause fog to form more quickly and more often than cleaner windshields.

– Reduce the Sources of Moisture in the Vehicle

This method is especially useful for those who own RVs, as wet items, laundry and even hot drinks can raise the level of humidity in the car. When the humidity gets high inside the RV, it condenses after coming into contact with the cold surface of the windshield, forming a fog.

Thus, you need to reduce moisture inside your vehicle by eliminating some of these sources. For instance, you can dry your laundry or drink your hot coffee outside to decrease the chances of fog formation.

– Use a Shaving Cream or Rain-X To Prevent Fogging

This may come as a surprise, but shaving creams can actually help you fix the fog problem in your car. First, spray a sizeable amount of shaving foam into your hands and smear it all over the windscreen. Now, allow the shaving foam to sit on the windshield for about 2 minutes, then wipe it with a clean dry cloth. The foam leaves a slippery surface; thus, the tiny droplets of water just slip off after forming on the windscreen.

However, the best product designated for preventing car windows fogging up inside when parked is Rain-X. This product adds a hydrophobic coating to the windshield, turning the moisture into beads of water that subsequently roll away. However, if you do all these but the fogginess still remains or you notice cracks on your windshield, call a mechanic for help.

Frequently Asked Question

– Why Are the Car Windows Fogging up When It Rains?

Car windows fogging up inside when it rains is because the temperature outside the vehicle is different from the windshield’s temperature. If it is warmer inside the car, it condenses and forms tiny droplets of water when it comes into contact with a colder windshield.

Foggy Windows on Car

Are Temporary Window Coverings Effective in Preventing Windshield Fogging in the Summer?

Temporary car window coverings can be a practical solution for preventing windshield fogging during summer. These coverings act as a barrier between the hot air outside and the cooler air inside the car, reducing condensation. By blocking the direct contact of humid air with the windshield, they help maintain better visibility and enhance driving safety.


Foggy windows when driving can cause low visibility and lead to road accidents, so knowing the cause is important but more essential is knowing how to fix them.

Here is a recap of all that this article has discussed:

  • There are several causes of fogging up, including temperature variances, high humidity, and the use of air conditioners, just to name a few.
  • One way to clean up the fog is by using a clean dry cloth, but a more efficient method is to use windshield wipers and wiper fluid.
  • You can also put on the A/C and heat simultaneously, ensuring that the heat is set to the highest so that both components can stabilize the temperature in and outside the car.
  • A very efficient method is to use Rain-X, which creates a hydrophobic coating that turns fog into droplets of water and rolls them down the windshield.
  • In the absence of the product, you can apply shaving foam, which also acts as a hydrophobic coating and prevents the formation of fog.

That’s how to get rid of fog on windshield when raining. If all these don’t work, then call on a professional for help defog windshield.

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