Nearly every driver has experienced their car windows fogging during a rainstorm – but do you know how to defog car windows in rain without AC?
Most of the time, the best way to clear a fogged windshield is with a warm defroster.
But what can you do if your car doesn’t have AC, or the AC doesn’t work correctly?
This article will tell you everything you need to know.
To defog car windows in the rain without AC, wipe off the condensation with a microfiber cloth, turn off the air recirculation, turn the defroster on low, and open the two front windows slightly.
Why Do Car Windows Fog in the Rain?
Your car’s interior windows get foggy in the rain because of water vapor condensation.
Condensation occurs when the water vapor in the air gets cool enough or saturated enough to return to a liquid state.
Rain occurs when the relative humidity in the clouds reaches 100 percent, meaning the air is so saturated with water vapor that it can’t hold anymore.
While the relative humidity on the ground may be less than 100 percent when it rains, the air is still heavily saturated with moisture on a rainy day.
If you’re wet from the rain, the moisture on your clothes, shoes, floorboards, and upholstery adds to the humidity level inside the car.
Your breath and sweat also release water vapor into the air.
Combined, all these factors can increase the relative humidity inside your car to the saturation point where water condenses on any hard surface in your car.
Rain is also generally cooler than the air inside your car. The rain falling on your windshield and windows cools the glass.
When the glass reaches the dew point, the temperature at which water vapor condenses, the moisture inside your car collects on the cool glass.
This leaves a film of condensation that blurs your vision.
How to Defog Car Windows in Rain Without AC
You have to act quickly if you’re driving in a rainstorm and your windows suddenly fog up.
Here’s how to defog your windshield when your AC doesn’t work.
Use a Microfiber Cloth
The first step in how to defog the windshield without AC is to wipe off the excess moisture condensed on the windows.
Any cloth will do, but for best results, keep a microfiber cloth in your car.
The texture of microfiber makes it more absorbent than other fabrics, as it can hold up to eight times its weight in water, and it leaves a streak-free window finish.
Turn Off the Recirculate Setting
The recirculate setting in your car reduces the amount of air that comes in from the outside.
This is great on a dry, winter day when you don’t want to waste energy heating cold outside air.
But on a rainy day, the recirculate setting causes the additional moisture from your clothes and breath to accumulate in the air.
Turning off the recirculate setting will bring more air in from the outside.
As mentioned earlier, the outside air is likely quite humid if it’s raining, but it’s almost certainly less humid than the air inside your car.
By turning off the recirculate setting, you can reduce the humidity level inside the car, resulting in less condensation on the windshield and windows.
Roll Down The Window Slightly
The more air you can circulate through your car and, most importantly, across the inside of your windshield, the faster the condensation will dissipate and the slower it will accumulate on the glass.
Opening both the front windows will create a cross breeze that enhances airflow inside the car.
The outside air moving over the gap in the window creates a negative pressure stream that sucks out the humid air from inside your car.
That, in turn, reduces the air pressure inside the car, pulling less humid outside air in through the opening in the other window.
Tip: Opening two windows increases airflow and prevents the uncomfortable air pulsation (the “wub wub wub” sound) caused by air trying to get in and out through the same opening.
Of course, you shouldn’t roll the windows down too far unless you want to be pelted by rain as you’re driving down the road.
But even a tiny opening in the two front windows can create enough air movement to defog windows on a rainy day without letting too much rain inside.
Turn Your Defroster to a Low Setting
The best thing you can do to clear windshield fog on a rainy day is to warm the windshield.
Ideally, you would do this with the car’s defroster, which blows warm air directly on the windshield. But if your AC isn’t working, that’s just not possible.
You can still use the defroster to defog the windshield, even without AC, as long as you keep it on low.
The air coming out of the defroster will be slightly warmer and drier than the interior air because it comes from the hot engine compartment.
You may be tempted to crank up the speed to clear the condensation faster, but that would be a mistake.
Fast-moving air will cool the glass more, counterproductively causing even more condensation rather than reducing it.
But keeping the defroster low will warm the windshield and circulate the air enough to reduce windshield fog.
Don’t Use Your Hands
Whatever you do, don’t wipe away the condensation with your hands.
Your skin’s natural oils can smear on your windshield, causing even worse visibility problems than condensation alone.
If you don’t have a microfiber cloth, just about any semi-absorbent fabric will do, including a towel, t-shirt, or napkin.
How to Prevent Windshield Fog
It’s great to know how to remove windshield fog, but it’s even better to prevent it from happening in the first place.
Fortunately, there are commercially available and homemade solutions that you can use to keep your windshield clean and fog-free.
Use Anti-Fog Products
You can buy commercial anti-fog windshield sprays and wipes that prevent condensation from happening in the first place.
However, it’s much less expensive to make your own at home using a mixture of white vinegar and water in a spray bottle.
Tip: Don’t spray the windshield directly when applying the anti-fog spray. Instead, spray the cloth, then wipe the windshield and windows with the damp cloth for a streak-free shine.
Use a Cheap Foaming Shaving Cream
Try this household cleaning hack in your car. People have been using foaming shave cream to prevent bathroom mirrors from fogging for years.
This same trick works on your windshield and car windows, too. Here’s how to use shaving cream to prevent your windows from fogging.
Tip: Stick with the cheap shaving cream, not the moisturizing kind, which may contain oils that can worsen fogging.
Step #1: Wash your hands carefully to remove any dirt and oils that might smudge your windows.
Step #2: Dispense a generous amount of shaving cream into the palm of your hand and spread it evenly across the inside of your windshield. Repeat on the interior windows, if desired.
Step #3: Allow the shaving cream to sit for up to five minutes.
Tip: Don’t leave the shaving cream on the windows for too long, as it can leave a sticky, foamy residue if it dries.
Step #3: Use a clean, dry, microfiber cloth (or a clean t-shirt) to wipe the shaving cream off the windows.
Step #4: Use a second clean, dry, microfiber cloth (not the same one) to buff the windshield and windows to a beautiful, streak-free shine.
Read Next: Can You Jump Start a Car in the Rain?
Final Thoughts
It’s essential to know how to defog car windows in rain without AC.
The best way to clear the fog from the inside of your car’s windshield is to use the defroster setting on warm.
But if your car doesn’t have AC, or if it just doesn’t work very well, Reduced visibility causes thousands of accidents each year, and a fogged windshield is a serious driving hazard.
Fortunately, there are things you can do in an emergency to defog the windshield without AC.
Wiping the glass with a microfiber towel and increasing air movement inside the car by cracking a window and turning the defroster on low will have your windshield dry and clear in no time.
