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How To Prevent Windows From Fogging Up

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Car Windows Fogging 1

We’ve all been there. You’re running late for work, so you jump in the car and you’re greeted with fogged-up windows. No matter what you try, it never seems to work. You wind up frustrated and driving in an unsafe manner. In this guide, we’ll talk all about fogged-up windows. We’ll tell you what causes them and how to prevent windows from fogging up.

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What Causes Windows to Fog Up?

The simple answer is that science causes your windows to fog up. It works in a few different ways to wreak havoc on your windows’ visibility. It’s mostly due to moisture, dust, temperature differentials, and using the wrong material to clean the windows.

Moisture in the Air

If there’s a lot of moisture in the air inside of your car, the glass will get foggy. In this case, it’s water droplets from the air settling on the glass and condensation.

The moisture can come from water sources within the car, wet clothes while you’re driving, or humid air. It’s always a good idea to shake yourself off a little before getting into your car when it’s raining or snowing out.

Dirty car window with dust and dirt visible on the front windshield

Dirt and Dust

One cause of fogging is a lot of dust and or dirt on your windows. Moisture is more likely to stick to dirty window surfaces. On top of that, debris also produces glare on your windows. Overall, it’s a terrible thing to have on windows.

Improper Cleaning

We’ve all been there – you get into your car and you’re in a rush. The windows are fogged-up so you quickly use your shirt’s sleeve and wipe it down enough so you can see.

This form of improper cleaning makes the problem worse over time. You’re not doing anything about the root cause of the fog. Not only is the dirt still present on your windshield, but now you added oil and potentially micro-scratches on the glass. Either of these will make the problem worse.

The best practice is to never use a sleeve, napkin, old rag, or your hand to wipe your windows.

A Temperature Differential

If the outside temperature is different than the inside temperature, your windows can fog up. The differential has to be serious enough for water vapor in the air to start condensing on the glass.

The warmer side of the glass will be the one that fogs up. This means that on hot days, you’ll get fog on the exterior which can increase fog on colder days.


How to Prevent Windows from Fogging Up

Knowing what causes the fog is one thing. The more important piece of the puzzle is finding out what you can do to get rid of this nuisance. Let’s take a look at some methods and materials you can use to kick fog to the curb.

Use a Window Cleaner on the Outside

A quick way to keep your windows clear is with a window cleaner. This clears away dust, prevents water from building up, and creates a smooth surface on your windows. By routinely using window cleaner, fogged windows will become a distant memory.

We always suggest using this one from rain-x because it works the best. This is the same company that sells windshield wipers, so they know their way around your car’s windows. We’ve tried a lot of different options, and so far this one has worked the best.

Rain-X 5071268 2-in-1 Glass Cleaner and Rain Repellant


Run the AC

In the dead of winter, the last thing you want to do is blast your AC. It works really well at de-fogging your windows through a little science. It takes the moisture out of the air and corrects the temperature differential on your window.

If you’re not a fan of the chilly air blowing on you, divert your vents and have them point at your windows. You only have to run it when the windows fog up, you can turn off the AC afterward.

Keep Your Air Recirculating

Another thing that leads to fog is stagnant air in your car. If it doesn’t have an opportunity to recirculate, it can lead to fog. Keep your vents open while you drive to help promote air recirculation.

Check your AC settings to see if you have a recirculate option and make sure you keep it on.

Close up of the car HVAC climate control system with air recirculation button engaged

Crack Open a Window

Cracking open your window helps with recirculation as well as the temperature gradient across your windows. As long as it isn’t raining, there’s nothing wrong with letting some natural air inside.

If the air in your car is warm and wet, then an open window will help usher it out of the car.

Clean the Windows from the Inside

Similar to one of our previous suggestions, you can always just use standard glass cleaner. The secret is to use it on the interior surfaces of all your windows. Rain-x works best for the exterior surfaces, and we always use Windex for the interior.

While using it, make sure you open the windows so the chemicals can vent out. Use a soft cloth and wipe in circular motions to get the best clean.

Windex 32 oz With Glass and Window Cleaner Spray Bottle


Use Kitty Litter (or a Desiccant Pouch)

Did you know that kitty litter can help de-fog your windows? It’s an absorbent material that’s pretty cheap and easy to use in your car.

We suggest filling a sock with kitty litter and leaving it on the floor somewhere. It will eat up some of the moisture in the air and reduce your chances of having foggy windows. Alternatively, you can use professional desiccant bags like those little silicon pouches you sometimes see in beef jerky bags.

A desiccant is just a material that’s awesome at absorbing tons of moisture. Like microscopic sponges, but better. Using enough of these will wick away moisture in the air. This is especially useful in places like Florida where the air is always humid.

wisedry 50 Gram [10 Packs] Silica Gel Desiccant Packets Microwave Fast Reactivate


Fix Your Car’s Heater

In some cases, window fog can be thanks to a faulty heater. If your car isn’t blowing hot air when it’s cranked all the way up, then there could be something going on under the hood.

Regularly foggy windows can be a symptom of a busted heating system in your car. Maybe it’s time to take a look or have a mechanic look it over.

Climate Control - Turning On The Heater

Check Your Car’s Thermostat

Similar to your car’s heater, the thermostat could also be a culprit. The thermometer is used to regulate temperature and keep air moving. It also stops water from circulating above a certain temperature. It’s a good idea to check out the thermostat while you’re at it – a replacement is pretty cheap and easy to do.

Check for Another Source of Moisture

If you’ve tried some other solutions and the problem is still persisting, take a look around your car. Feel your floor mats, and the fabric seats, and look for sources of moisture.

If you have constantly wet floor mats, then they could be the reason why your windows keep fogging up. It’s easy enough to clean, dry, and replace these mats.

You could also have a leak within your heater matrix or cracks in your windows’ seals. Anything that causes extra moisture in your car needs to be dealt with.

Use a De-Icer

For our friends in colder areas, do you have a quality de-icer? As you know, ice is a form of water that adds extra moisture to your car. It also provides a cold exterior for your window. As you warm up the inside of your car, the ice will make a temperature gradient that creates fog.

Hit your windows with a de-icer spray to get rid of the morning frost and kiss fog goodbye.

Sprayway SW758 Industrial De-Icer 16 oz


Replace Your Chipped Windshield

A chipped windshield is really dangerous, but it can also be the cause of your foggy windows. Temperate air and moisture have a free ride into your car through a cracked windshield.

Use a High-Quality Towel

If your towel has any hard materials or defects on a microscopic level, you could actually make your fog problem worse. On top of that, oils and the wrong material in a low-quality towel or rag will also make things worse.

The solution is to use a high-quality towel that’s designed specifically for automotive glass use. Our team only uses Diamond Glass brand towels. This is another area where we did plenty of trial and error, and nothing came close to the result we saw with these. They’re affordable and perfect to use on your windows and mirrors.

Diamond Glass Microfiber Window and Chrome Towel 16in x16in – 4 Pack Blue


Keep Your Hot Coffee Covered in a Thermos

Another surefire way to fog up your windows is to have an open container of hot liquids. The steam produced will go right to your windows and start fogging them up.

Just grab a covered thermos and make your life easier. We would never suggest you get rid of hot coffee – that’s impossible!


You just learned more about fog in your car. At this point, you know what causes it and you have a handful of solutions to try out. You don’t have to drive with your head sticking out of the sunroof to get to work anymore. Keep those windows fog-free and your boss won’t have to yell at you for being late ever again!

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Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

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