Why your car windows are steamed up in the morning & how to fix it

Mist, fog or condensation is annoying when you just want to get to work in the morning. So lets look at the causes and what we can do about it.

What causes car windows to steam up?

Your car windows fog up in the morning because there’s moisture trapped inside the vehicle. When the outside temperature drops, it cools the windows, causing the warm, damp air inside to condense on the cold glass. This condensation is what creates the fogging of your interior glass.

As the winter goes on, moisture builds up in the car over time from the moisture in your breath, wet shoes and damp jackets. Heated windows just evaporate the water droplets and increase the humidity within the car.

Morning dew on the outside of the car is a different problem, which can be equally annoying. Don't worry, we will cover the subject further down the page.

But why is my car steaming up when I'm not in it?

There are usually two main reasons you find your windows are suddenly hard to get clear. Let us address the most serious first.

Leaks

Water could be getting into your car because you have sprung a leak. If your car is around eight years old or older, some of the seals, grommets and membranes may have perished and are letting in water. This is very common on cars of this age.

If you are finding you have large droplets on the inside of your windows, rather than mist, it is likely there is a lot of water in the car, and you probably have a leak.

If you park under a tree and dead leaves and other debris fall on your car, there is a reasonable chance that scuttle or sunroof drainage holes have become blocked and are causing water ingress.

If you have had any repairs on the car in the last year, crash damage or a replacement windscreen, it is possible the work wasn't done properly and has caused a leak, which is why you suddenly have fogged up windows this winter.

So, before going any further, go check your car for signs water is getting. Make sure the carpets aren't soggy and that there isn't a puddle under the boot carpet.

If you find evidence of a leak, you will need to get it repaired and the car dried out, and that should solve your problem.

Short Journeys with wet kids

Your heater/ air conditioner / climate control can help to dehumidify your car and under normal circumstances will dry out your car, but it needs a little bit of time to do it. If you do many short journeys, popping down to the local shops, the school run twice a day, five days a week, then the car never really gets a chance to get warm and dry out.

If you are picking up a hoard of kids with wet shoes, wet coats, and have the dog panting away in the back, you are introducing water to the car with every journey. This is compounded in winter condition if you have snow on your boots and shoes.

It might take fifteen minutes for the car to get properly warmed up, so if you only have a twenty-minute journey, your heater only gets five minutes to dry the car.

Broken Air Conditioning

And air conditioner should remove moisture from the air, but if the system is not working properly, it could make things worse. It is not unknown for them to leak fluid, or the evaporator drains can get blocked. Check for damp in the front footwells, especially if you smell a sweet smell, musty or rusty odours. If your car is a few years old, you may want to consider having your air conditioner serviced and recharged.

What is the quickest way to clear misty windows?

The best way to clear your windscreen is with the car's heater. It is highly recommended that you take time to learn your car's heater / air conditioner and know what all the buttons do, and ensure you are using it properly and that it's on the right settings.

I don't mean to sound patronizing, but say this as somebody who had a fight with my car's heater not so long ago before parking up and realizing that I had it pointing at my feet instead of the screen. I blame the wife, who suffers from cold feet and keeps messing with the settings.

If you have climate control / air conditioning, there may be all sorts of settings, some of which may be specifically for clearing the car's glass, so it may be worth having a read of the manual.

If you don't have air conditioning, then it is recommended to set your heater for windscreen, turn it down to a low temperature and gradually turn up the heat. This is at least the perceived wisdom, but even if this does make a difference, it is doubtful that many people have the patience or want to be fiddling around with the heater when they are freezing cold first thing in the morning. You just want to get warm, get demisted, and get going. So we would suggest whacking the heater on full, and instead we will look into some other ways to clear your windscreen fast and effectively.

Wiping the windscreen

There are other, inferior articles on the internet that advice against wiping your windscreen down with a cloth because it can leave smears. We disagree. While you are sitting there waiting for the car to warm up, you may as well wipe the windows down.

However, we don't recommend doing this with the back of your hand. It doesn't work and if you have diamond rings on, you can cause permanent scratches to the glass. We see damaged glass often enough that it's worth mentioning.

Instead, we recommend getting two, large, good quality microfibre cloths. Preferably, ones especially made for glass.

There are several really good reasons to do this. Firstly, if you wipe down the insides of your windows regularly, they will be clean. Clean glass tends to condensate less and clear faster than dirty glass. Secondly, giving your windscreen a wipe over will warm you up. It will also mean that you are less tempted to drive off with foggy windows, which can be a criminal offence. 

Why would we recommend having two cloths? Because once you use a cloth, it will become wet and if you leave it in the car, as it dries out, it puts all that moisture back into the air, which will condensate again tomorrow morning. We recommend removing the damp cloth from the car and putting it on a radiator indoors.

I keep one on the radiator in the hallway, where I keep my car keys. Should I forget it in the morning, that's no problem because I have a spare, one in each front door pocket.

Removing moisture from the car

Firstly, find the recirculate setting on your heater and turn it off. Recirculate reduces the amount of fresh air coming into the car and recirculates the air you already have. This is useful on a cold day when you want to heat the car. The car will warm up far quicker if you are reheating air instead of pulling in new cold air. The problem is that the air in the car is humid and laden with water. So turn it off and get some fresh air in the car, at least until the windows are clear. You can also open the windows or just air the car out by opening up the doors, although not while the car is in motion, obviously.

Don't leave anything wet in the car overnight. If you use an umbrella, dry indoors. Don't leave wet coats or sports bags in the car.

Dehumidifying your car

The dehumidifying pods that you can buy from most supermarkets work exceptionally well. They are a plastic pot with silicate crystals in the top, which draw in moisture which then fills the pot full of water so that you can see that it's working. The problem is that you then have a plastic pot full of water in your car, and they aren't really designed to stand up in a moving car and will fall over, spilling the contents all over your carpet. If they happen to fit nicely into the map pocket of your door, then they might work for you. They can also be tapped together to make them more stable, and placed under the seat. This works unless somebody gets in the back and kicks them over.

However, you can get dehumidifier bags which are reusable. You just bring them indoors and dry them out. You will probably need a couple, which like your cloths, you alternate as you dry them.

An alternative is to use cat litter which is super absorbent and will pull moisture out of the air, especially the silicate crystal type. Some people recommend that you get some old tights or socks and fill them full of the cat litter and place them somewhere in your car. However, I have found that just having the cat litter back in the boot of the car with the top open works very well, as long as you secure the bag so that it doesn't fall over. It's a cheap home remedy fix.

Electric portable dehumidifiers will also help, but you will need access to a power supply, which is easy if you can park the car in a garage. But if you were parking in a garage, you likely wouldn't have this problem in the first place.

These solutions will work if the cause of your misty windows is hot breath, wet kids and short journeys, but if you have a leak in your car, you could have several gallons of water under your carpets and the only way to solve this is to lift the carpets and suck it out before having your car professionally dried.

Glass coatings

While we are on the subject of home remedies, there are people who will suggest using shaving foam on your windows to stop them misting up. Just don't do this, please!

Yes, it is true, that some people who wear goggles, especially when they are getting hot and sweaty playing sports, have in the past coated the inside of their visors and goggles with shaving foam, washing up liquid, baby shampoo, toothpaste or potato to prevent misting, but this is no longer the 1970s. There are products for this which are cheap, easily available, and far less messy than shaving foam.

Regardless of what you put on glass to stop it misting, it only works to a point. For the most part, the best you can say is that they will help the glass clear more quickly. After years of trying different products, we have never found anything that is certain to prevent windows from getting steamed up. So at best a coating will help, but it won't solve the problem.

There is also a bit of a paradox here because glass cleaners contain strong solvents to remove anything coating the glass, then evaporate to leave no residue so that the glass is clear without streaks or smears. Most glass coatings do the opposite and work because they leave a waxy residue. So if you use a glass cleaner, and we recommend you do, it will strip off any coatings.

With all that said, an anti-fog product such as Rain-X can be bought for less than £5 in the supermarket and makes enough difference to be worth it. Diamondbrite is another product we have used for years and works very well.

A bonus of these coatings is that on those very cold morning when we get a frost, they make it much easier to clear your windows.

Plug in heaters

You can also get little heaters that will plug into a cigarette lighter, which you can direct at your windscreen.

This kind of thing has been used for years in countries which regularly have sub-zero temperatures in the winter, and the more sophisticated set-up can be set on a timer to warm your car half an hour before you get in it.

Thanks to the wonders of global trade, these can now be bought for as little as £7 on eBay, however some of the marketing pictures for these products show them shooting out flames, which is my worst fear when buying cheap electrical goods from China!

We would recommend you pay a bit more, buy them from a reputable outlet, don't use any double-sided tape to stick them to your dashboard (it will mark and ruin the dashboard) and be careful.

Hot air can melt plastic and a sudden temperature change can shatter cold glass. We would recommend you do not point them directly at your windscreen on very cold days.

Summary

Steamy windows are caused by a build-up of humidity inside your car, which condensates on the inside of windows on cold morning.

Causes of Window Fogging

• Moisture inside the car: Warm, damp air condenses on cold glass, causing fog.
• Winter moisture build-up: Comes from breath, wet clothing, and shoes.

Common Reasons for Persistent Fogging

1. Leaks: Often from ageing seals or blocked drainage, allowing water inside.
2. Short journeys: Frequent short trips prevent the car from drying out, especially with wet passengers or pets.
3. Broken air conditioning: Can worsen fogging if not removing moisture effectively.

Quick Ways to Clear Fogged Windows

• Heater use: Learn the correct settings to efficiently clear the windscreen.
• Wiping windows: Use quality microfiber cloths to prevent scratches; store the cloths outside the car to avoid reintroducing moisture.

Reducing Moisture in the Car

• Turn off  heater's recirculate: Brings in fresh air to reduce humidity.
• Run your air conditioner in the winter: It will remove moisture.
• Air out: On a dry day, open up the doors and let the damp air out.
• Avoid leaving wet items inside: Dry umbrellas, coats, and sports bags indoors.
• Use dehumidifiers: Disposable or reusable options, like silicate crystals or cat litter in socks, absorb excess moisture.

Additional Tips

• Glass coatings: Anti-fog products like Rain-X lessen fogging and help glass clear faster.
• Plug-in heaters: Small, car-safe heaters can quickly warm windows before driving.

Morning Dew on Exterior Windows

I'm sure we have all experienced the problem on a cold morning where we dash to the car and start it up to get that heater going. We sit there shivering, waiting for the windows to de-mist, only to find that when it does, we still can't see out of the windows because of the dew on the outside. Windscreen wipers clear the front and back windows, but not the sides, so we try winding the windows down in the hope that it will clear it. We might even drive as far as the duel-carriageway and find that our wing mirrors are covered in water droplets.

There are several answers to this problem. The first is to use hydrophobic coatings. We specialize in permanent ceramic coatings which go over the whole car, and we can't recommend them highly enough, these will do the job perfectly, but if you just want something for your windows, we recommend Rain-X or one of the many other similar products available. Turtlewax makes one called Clearvue, and Bluecol, Diamondbrite, Autobrite and Gtecnique also make them, so you should have no problem finding one online, at your local motor accessory shop or even at the supermarket. 

They are easy to use, just make sure your windows are clean, you wipe it on, wipe it off again, and it then leaves an invisible coating on your glass that repels water. You should now find that you will have a lot less water blocking your view, and it should fall off easily once you start to drive along.

We do not recommend you use this on your front windscreen because, with the water unable to stick to the glass, it instead puddles around your windscreen wipers when they are in use, and you are travelling below about 30mph. Some people don't mind this, but it can be annoying.  Instead, you might want to use Rain-X windscreen washer additive.

Exterior glass coatings of this type last a couple of months before you need to re-apply them, and while they work they are a considerable help. However, they won't completely clear your windows, and especially not your wing mirrors.

If you want your windows and mirrors completely clear before you drive off, the only way is to get out and clear off the water. For this, we recommend a "water blade", otherwise known as a "squeegee". These are what people who clean windows for a living have used for decades, and they are the best way to dry glass. They are cheap and easy to get hold of, and these days they make them from silicone instead of rubber, which is far better stuff.

You only need to clear your side windows and wing mirrors, so you won't need a huge one. 

Bonus tips for exterior glass & mirrors

As previously mentioned, you will have less condensation if your glass is clean, so we recommend cleaning your windows.

A lot of people seem to struggle with this because they buy a bottle of glass cleaner, spray it on and give it a wipe. What happens is you are just pushing the dirt around. If you want clean windows, you need to wash them. Get a big moist cloth with soapy water and give them a good wash down, getting right into the corners. Then you can use a glass cleaner to get rid of streaks and smears.

Make sure your washer bottle is full up, and don't just use water. A good quality screen wash makes all the difference, you don't have to go hunting for them or pay a lot of money. You can pick up a bottle of screen wash in the supermarket. While you are doing this, make sure you have antifreeze, de-icer and an ice scraper.  For most of the year, you don't need these things, but you will be grateful when you do.