Fog is dangerous enough when it’s looming over the road, but it’s even worse when it’s on your windshield. A lot of drivers will experience this as they drive through a rainstorm, but how do you stop it?
It’s all a matter of counteracting the science that causes fog. This entails making the inside of your car the same temperature as the outside. If it’s warm outside, turn on your warm defrosters. You can also crack a window and use your wipers to help. Be sure to keep the inside and outside of your windshield clean and fog will dissipate quicker in the future.
In this guide, I’ll get to the bottom of things. I’ll explain how to get fog off a windshield when it’s raining and get into the science behind the fog. I also have a number of preventative methods to try to keep fog away in the first place.
Why Fog Happens
Fog happens when cold and warm temperatures meet each other on a surface like glass. In your car, you’ll see fog on your windows, dash, and windshield since these are the glassy surfaces within your cabin.
In the case of your windshield, it has to do with a difference between your cabin’s temperature and outside temperatures. If it’s a cold, wintery day and you have your heater on, that change in temperature can cause fog.
When it’s raining, there’s another piece of science at play: condensation. Rain is wet which means it has a high level of humidity. The outside of your windshield is highly humid, and the inside of your car isn’t. As a result, condensation will build on the inside of your windshield.
Even though both forms of fog can look alike, the way to fix the problem is very different. In the rest of the article, I’ll give you tips that will fix either form of fog, so you should have a complete solution by the end.
Fog Is a Big Problem
When it comes to a foggy windshield, there’s a lot that can go wrong. As you know, looking through your windshield is the only way to see the road in front of you.
With fog, you won’t be able to see anything. This is an incredibly unsafe position to be in, especially as you’re driving along.
To make matters worse, there’s no hands-free way to remove fog. That means that you’ll need to start looking around your cabin and reaching for dials while still driving down the road.
The Safest Way to Remove Fog
I’ll talk about 6 different ways to get rid of the fog in a second, but I want to make this disclaimer: you shouldn’t attempt any of these methods while still driving. The very first thing that you should do is pull over.
Once you’re on the side of the road, you can start trying different methods to get rid of the fog. If you try doing this while driving, your windshield can easily fill up with even more fog and further ruin your vision.
6 Ways to Get Fog Off a Windshield When It’s Raining
Now that you’re pulled over, you can start working through these tips. Below are 6 ways that I’ve personally used to get fog off a windshield when it’s raining. There’s a little trial and error that goes into it, but I’m confident you’ll find an option that works.
1. Open the Windows
The first thing that I usually try is to open a few windows. Remember, the fog is caused by a difference in temperature between the inside and outside of your car. By opening a window, you’re allowing outside air to come into your car.
It also helps by giving some additional airflow through your car. When the air gets too stuffy, fog can get even worse, so opening a window helps on two fronts.
During a rainy spring season, you might pass a lot of drivers who have their windows slightly cracked. There’s a good chance they’re doing that to avoid fogged-up windows.
2. Stop Recirculating Air
If you look at the different buttons for your HVAC system, you’ll find the “recirculate” option. The symbol for this button usually involves an arrow doing a 180.
When your HVAC is on recirculate, there’s a damper that shuts within the system. It closes off outside air. Instead, your car will start circulating inside air over and over, instead of getting new air from outside.
By creating a closed-loop, the humidity and temperature within your car will continue to get worse. Remember, you want the inside of your windshield to be about the same temperature and humidity as the outside of your car.
For that reason, you should turn off your recirculation setting if it’s turned on. You want to make sure new air is coming in.
3. Use Your HVAC to Match Outside Temperatures
This option might be the most uncomfortable, but it’s personally worked really well for me. Since your windshield is responding to a difference in temperature inside and outside the car, you should force your car to match the outside temperature.
If it’s really cold outside and it’s comfortably warm in your vehicle, fog will form. This step entails turning on the AC and making it colder inside of your car.
You don’t need to do this for the entire trip, just long enough for the fog to go away. Once the glass de-fogs, then you can go back to a more comfortable temperature.
4. Use Your Wipers
If the fog is outside of your windows, the wipers will help. Since it’s raining, you should probably have them on anyway.
If there’s not enough rain, make sure you use some windshield wiper fluid before running your wipers. Running wipers on a dry windshield is a quick way to prematurely kill your wipers.
This solution won’t help you if the fog is inside your windshield.
5. Try the Defrosters
Your defrosters are a great way to stop fog from ruining your vision. They work by re-routing air directly to the base of your windshield. That means that you won’t feel any warm air coming from your face or leg vents. Instead, the air gets shot at your windshield.
It’s important that the defrosters are set to the same temperature that it is outside. When they start working, you’ll notice the fog disappearing from the base of your windshield and working its way up.
I would recommend that you first set your HVAC to come out of the face vents. Use your hand to gauge the temperature. When it feels cold or warm, then turn on your defrosters.
If you swap to defrosters prematurely, the air at the wrong temperature can blow out and make the fog even worse.
6. Wipe the Interior of Your Windshield
If you use your wipers and the fog doesn’t change, you probably have fog inside your windshield. Fixing this problem is easy enough.
Grab a microfiber towel and just give your window a wipe. This can be done in a few seconds; it doesn’t have to follow any special process.
This is just a temporary fix until you get sometime later to do a full fix (which I’ll describe later). However, it will do a great job of temporarily keeping fog away and restoring your vision.
Ways to Prevent Fogging Windows in the Future
If you want to try some ideas that will prevent fog in the future, I have some good news for you. I put together this shortlist that has exactly what you’re looking for.
Wipe Your Shoes Before Getting in
I’ve already established that fog can form from humidity. Did you know that it doesn’t just have to be humidity outside of your car? If you get into a car with wet shoes, then the moisture from your shoes can actually cause your windows to fog up.
It’s an interesting phenomenon that people surprisingly don’t know about. It is also very time-appropriate if you’re blaming the fog on the rain outside. Since it’s raining, you probably walked through some puddles to get to your car. If your shoes are soaking, then they could be causing the fog.
Before getting into the car, bang your shoes together to get rid of any excess water. I know that it’s not feasible to fully dry your shoes before you start driving, but doing the best that you can, will maximize your chance of avoiding fog.
To avoid condensation-based fog, you need to minimize how much water is on your windshield. As water droplets pool up on the glass, the glass will get even more fogged.
I recommend using Rain-X to help. I routinely do this on my cars and it helps a lot.
Rain-X is a windshield treatment that turns the glass into a hydrophobic surface. Instead of pooling up, the water droplets will slide away from your windshield.
Doing this will also extend the life of your wipers, so it’s a win-win. The only downside is that you might experience a squeak after the application. In this case, it’s not a bad squeak. You’re just hearing rubber sliding along the polymer-based layer of Rain-X on your glass.
The bottle will tell you how often to apply this treatment. You just use a towel and the spray bottle to put the Rain-X on your windshield.
Maintain Your HVAC System
If you turn up the defrosters and nothing happens, there’s a chance that your HVAC system needs to be maintained. If you want to take on the repair yourself, go through some troubleshooting steps to pinpoint the problem. The HVAC system is conceptually easy to understand but it has a lot of moving parts.
It might be easier to take your car to a mechanic to have them diagnose and fix your HVAC system.
The reason why this helps prevent fog goes back to the issue of temperature. After reading this guide, you should know the right temperature to shoot at your windshield to get rid of the fog. If your HVAC isn’t blowing hot air despite being on the hot setting, then the fog will just get worse.
If your heater isn’t working, then you can follow my guide. It’s still possible for your defrosters to not work even if your face vents do. With your car warmed up, turn on the defrosters and reach your hand near the vents by your windshield to see if the right temperature is coming out.
Use Glass Cleaner on Your Windows
Fog will stick around longer on a dirty windshield. Grime, oil, and dirt will prevent the fog from disappearing even after you turn on the defrosters.
If you want to prevent fog in the future, you should use a glass cleaner on your windows. Whereas the Rain-X glass cleaner also repels water, this one by Chemical Guys is glass cleaning only but does the job.
When applied to your windshield, it will get rid of all the debris on your glass, making it easier to remove fog in the future. Glass cleaner can be used inside and outside on all of your windows, but make sure you avoid contact directly on your car’s topcoat. It can melt the paint and lead to costly repairs.
It’s safe to use on both the interior and exterior sides of the glass.
Try Shaving Cream on the Interior Windows
If you don’t want to use Windex, you can simply use shaving cream. This treatment should only be used on the interior of your windows, not the outside.
The shaving cream adds a lubricious layer of protection to your windshield. This layer prevents condensation from building up, so you won’t have to worry about interior fog during the next rainstorm.
You can just use a microfiber towel to apply the shaving cream to the inside surface of your windshield. Grab a dry microfiber towel and wipe it down afterward to finish the treatment. Just like that, you have a protected windshield.
I would suggest sticking with a scent-free option. Using a minty shaving cream means that you’ll be driving around with concentrated scents around you all day. It could be pretty distracting and might lead to migraines and general annoyance.
What Not to Do When Fog Happens
I mentioned a lot of different ways to remove and prevent fog, but I should also talk about what not to do. This section is about things to avoid doing when there’s fog on your windshield during a rainstorm.
Don’t Rub with Your Hand
If the fog is on the interior of your windshield, there’s a temptation to just rub it away with your hand. It might even get rid of the fog right off the bat.
The problem occurs in the future. After rubbing your windshield, oils from your skin transfer to the glass. As I mentioned earlier, oil, dirt, and debris will make fog much worse in the future.
In my experience, wiping a windshield with my hand only worked for a few minutes. The fog would come back, and it would be even worse thanks to the added oils.
Don’t Keep Driving
I can’t stress the importance of pulling over when your windshield gets foggy. It becomes very dangerous if you try to remove fog while still driving at highway speeds with limited visibility.
A lot of times your windshield will fog up when you first get in. Before driving away, take a few minutes to ensure the fog is dealt with.
Don’t Use Napkins, Clothes, or Random Towels
If you don’t use your hand to wipe your windshield, you might want to try various objects around your car. I’ve seen a lot of friends use random towels, clothes, or napkins to get rid of fog on the inside of their windshield.
This isn’t a good idea.
First off, any of these products can have some inlaid debris that scratches up your windshield. A small piece of metal or plastic that is stuck in a towel can do lasting damage to your windshield.
In addition, you don’t know if the materials are compatible with your car’s windshield. Glass is a pretty unforgiving surface. If you use a towel that’s too stiff or aggressive, you could ruin your windshield.
Replacing the glass is much more expensive than using a clean and specific microfiber towel.
Snow Brushes and Ice Scrapers Will Do Nothing
Finally, make sure you don’t consider using your snow brush or ice scraper to get rid of any fog. Ice scrapers won’t work on the inside of your windshield because the curvature is different.
As far as snow brushes, you don’t want to transfer any debris to the interior of your windshield. If you have contaminants stuck to the brush, you could scratch your windshield.
These 6 tips will help you get fog off your windshield when it’s raining. Be sure to pull over before attempting any of them so you can stay safe. When you’re done, go through my preventative steps to keep fog away in the future. If you want more DIY guides, explore my site. Also, check out my list of car products that I highly recommend.