Does Rain Actually Clean Your Car?


If you live in a rainy climate, you might think you can get away with cleaning the car less because the rain will wash the dirt away. Unfortunately, this isn’t really the case, and rain often makes your car much dirtier. In this article, I’ll explain why, and give you some tips on how to keep your car clean and shiny. So let’s get started!

The Quick Answer

Rain will not clean your car because the pressure is too low to remove dirt and traffic film. Effective cleaning requires car shampoo and higher pressure water. Rain will actually make the car dirtier because it contains purities and lead to water spots.

Now let’s take a look at these reasons in a bit more detail, and talk about what to do instead to keep your car clean and shiny.

The Pressure is Too Low to Clean

Of course, pretty much everyone uses water to properly wash their car. So what makes rain water any less effective?

There are a few reasons behind this, but one of the main reasons, is because the pressure is simply too low to properly clean the paintwork, glass and trim.

To actually wash away dirt and dust properly, you need to things:

  • Surfactants and cleaning agents (found in car shampoos)
  • High pressure water

Rain is usually very low pressure, especially compared to power washers or even hoses with nozzle attachments. This means it rarely actually washes any dust or dirt away.

Rain Water Is Dirty

Rain water isn’t pure, and is actually quite dirty. It’s full of contaminants that are collected throughout the water cycle.

Heat from the sun causes water on the Earth to evaporate from various places such as plants, oceans, lakes etc. This water vapour rises and forms clouds. When the clouds become too heavy, the water droplets fall, which causes rain!

It’s during this cycle, that the water collects impurities such as dust, minerals, chemicals and dirt. So when it rains on your car, it’s essentially getting covered with impure water.

It Causes Water Spots

The impurities in the water cause a problem when it evaporates on your car. This leaves behind water spots which look like chalky residue on the paintwork, glass and trim.

They may seem harmless, but these water spots can actually cause permanent damage to the paintwork on your car. The chemicals and impurities left behind by the rain can corrode the paint if left to sit on there for too long, or in high temperatures.

This causes “etching” which means that the paintwork erodes away leaving permanent damage.

water spot damage

So not only does rain not clean your car, but it can actually damage the paintwork. Keep reading to find out how to protect your vehicle and keep it looking clean and fresh.

Important Tips to Consider

So if rainwater doesn’t wash your car, what should you be doing instead to protect your vehicle and keep it clean? Here are some tips to consider.

Apply a Wax, Sealant or Coating

Applying a layer of paint protection in the form of a wax, sealant or coating will help to prevent water spots and stop as much dirt, dust and contaminants sticking to the paintwork.

There are so many different types of products out there. My personal favourites for beginners are:

  • Meguiar’s Ultimate Wax
  • Sonax Brilliant Shine Detailer

These are two products I started out with that are very affordable and do a good job at protecting the paint. However there are many others that are a bit more expensive, but really great quality.

Check out my recommended products page to find out more.

Rinse the Car After it Rains

Rinsing the car with a low-pressure hose after it rains, if your car has a good wax or sealant on, will help to remove a lot of the surface water and prevent water spots.

This is because it essentially collects all the water so it “sheets” off the car all together. Water molecules are known as cohesive, which means they stick to each other.

Wash the Car Properly

The best way to keep your car looking fresh, it to wash it regularly, using the right techniques and tools. Using the wrong equipment, like sponges or brushes, and taking your car to an automatic car wash, will cause tiny scratches and swirls in the paintwork causing it to look dull. Ideally, you should wash your car at least monthly to keep it in good condition.

Check out this complete guide to washing your car without causing scratches.

More Frequently Asked Questions

Don’t worry if you still have some more questions. Here are the answers to some of the most frequently asked questions about washing your car and the effects of the rain.

Does rain wash away car wax?

Rain will not wash away car wax, but it will cause it to degrade more quickly. Cars that are stored outside and subjected to bad weather, will need to be washed and waxed more frequently to keep them clean and protected.

What happens if it rains after you wash your car?

If it rains after you wash your car, try and rinse it with low-pressure after it has stopped raining to help remove most of the surface water that has formed beads. The best thing to do is wash your car every 2 weeks to keep it clean and prevent water spot damage.

Is it okay to wash your car in the rain?

It is okay to wash a car in the rain as long as you are not using an electrical equipment (such as a pressure washer) and wear appropriate clothing to keep warm and dry. Keep in mind that the rainwater should not be used as a substitute for free-flowing water from a hose or pressure washer.

Thanks for reading! I hope you’ve found this article helpful. Don’t forget to take a look around the rest of the website to learn everything you need to know about car care.

Check out the Auto Care HQ YouTube Channel

Heather

I first became interested in car detailing around 3 years ago and learnt all the main techniques on my very first car. I spend a lot of time detailing my current car, and trying to keep my family's cars looking presentable too!

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