3 Simple Reasons Why Rain Causes Water Spots

Rain is the primary source of water, without which life is impossible.

However, as essential as this natural element is, its water presents myriad negative effects that most car owners know too well.

The last time your car was rained on, you later noticed some pesky water spots which you thought would easily be wiped off.

Unfortunately, these turned out to be stubborn stains that left you wondering; does rain cause water spots?

Rain water causes water spots because it’s not pure and carries many harmful contaminants. When rainwater droplets remain on your car surface, the liquid part evaporates, leaving behind the mineral residue in the solution. This residue then forms a hard water spot that is difficult to remove.

In this article, we shall delve deep to learn more about the effects of impure water, particularly rainwater, on your car’s surface. Read on.

Does Rain Cause Water Spots?

Rainwater is an electrolyte mixture containing varying amounts of minor and major ions that can react with other elements to form simple or stubborn car water spots.

The minor ions are silica, alumina, iron, boron, bromine, and iodine, while the major ones include sulfate ions, bicarbonate, chloride, calcium, magnesium, potassium, and sodium.

Nitrogenous compounds like nitrogen, nitrite, nitrate, and ammonia are also in the mix.

Rainwater is soft and harmless, but as it comes down, it picks along particles like chalk, lime, smoke, pollutants, pollen, and dust that can react with your car paint to form water spots. 

Several reasons explain why rain causes car water spots and damages car paint. They include:

The Acid Rain

According to the Environmental Protection Agency (EPA), acid rain is a broad term that means rain is contaminated with more nitric and sulfuric acids than normal.

These higher acidity levels, alongside other impurities, can damage your car paint by causing water spots if left unchecked.

Rain gets a lesser percentage of its Nitrogen dioxide (NOX)  and Sulfur dioxide (SO2) from natural sources, including volcanoes, but most of it is from human activities such as:

  • Regular vehicles and heavy equipment, i.e., earthmovers
  • Fossil fuel burning (for electricity) and electric power generators
  • Industrial activities, i.e., manufacturing

The wind blows clouds saturated in nitric and sulfuric acid over long distances, turning acidic rain into a cross-border problem, not just for those living around the sources.

Hard Water

To capture the relevance of hard water in this topic, you must recall and appreciate that all water, no matter its chemical state, owes its origin to rain.

As we saw a little earlier, most rainwater is soft at the source and only starts changing once it picks up impurities and other contaminants.

For hard water, the soft rainwater usually picks up dissolved atmospheric carbon dioxide to make it a bit acidic (different from acidic rain).

On reaching underground, carbonic acid dissolves soluble rock minerals like magnesium and calcium to increase its hardness.

Aluminum, iron, manganese, and a few others also dissolve to enhance the water hardness.

If you live in a hard water zone, you must have already seen the difficulty in making a lather when combining it with soap.

But, this water’s notoriety does not end there because its precipitation causes unsightly marks in baths, basins, toilet bowls, and kitchen utensils.

In the worst-case scenario, the mineral deposits precipitate within the pipe waterways, resulting in costly pipe blockages.

Now, pause for a second and imagine; if these are the effects it poses on the domestic front, how badly would hard water ravage your car paint?

Pollutants and contaminants

Although rain is celebrated everywhere, not all car owners are happy with it at the end of the day.

Once the clouds release it, the pure water falls as it gathers airborne pollutants and contaminants.

Eventually, rainwater will evaporate, leaving back a layer of chemical compounds.

When these residues come in contact with sunlight, the ensuing reaction is strong enough to mess up your car’s paint.

Typically, the paint may crack, leaving irregular outlines on your car’s surface. Worse still, it may peel, exposing your vehicle to other elements like rust.

Water drops on blue surface (a bit grainy because of metallic car paint)

Is Rain Bad for Your Car Paint?

When it rains, it is easy to see the water flowing down your car’s surface and assume all is well.

You may even feel good if your car is overly dusty because it is getting a free wash after all.

But, is rain good or bad for your car paint?

Car paint and rain don’t always work well together. The chemicals, pollutants, and acid rain can deteriorate the clear coat and the underlying body paint if exposed and left unattended.

Rainwater affects your car paint in several ways:

Mineral deposits

Also known as hard water spots, these are the spotted chemical residues that remain on the car’s surface after the water has evaporated.

These occur mainly when you fail to wipe the water off your vehicle after a downpour.

Mineral deposits will also form if you use undistilled water from the taps and sprinklers.

Etching marks or chemical etching

If left unaddressed, the dirt and other contaminants latching on the paint continue eating into the paint to cause cracks and peeling in a process called etching.

Typically, this is the deteriorated version of mineral deposit water spots.

Muddy rainwater

If you drove under rain showers while wading through flooded streets, cleaning the car as soon as possible is important.

Mud and other ground dirt add impurities to the water, making it even more harmful to your car paint.

Can Rain Mess Up Car Paint?

It is difficult to tell whether the rainwater is clean or contaminated when it rains.

Therefore, leaving the rainwater deposits to dry off your car surface would be risky.

But can rainwater really mess up your car’s paint?

Rainwater can mess up your car paint because it is usually acidic or contaminated with impurities and other pollutants. Falling rain, running groundwater, and piped water pose an equal risk to your car paint because of these acquired chemicals.

More recently, contaminated rainwater has been in the records for affecting marine life and even killing trees.

Today, late-model car owners are also lamenting because of the ravages it is causing to their car paint. 

For late-model car owners, the problem is compounded by rampant pollution and the recent mass adoption of the clear coat, a high-gloss car paint technology.

Its finish creates a mirror-like sheen, and most car owners are going for it.

However, paint companies and car manufacturers say the finish is highly susceptible to marring by pollutants, particularly acid rain.

Speaking to the New York Times, top car paint producer product manager P. Gallagher (E. I. du Pont de Nemours & Company) said, “It tends to highlight all the defects.”

While addressing the same issue, spokespeople for the Ford Motor Company, Honda Motor Company, the Chrysler Corporation, and General Motors Corporation were unanimous about acid rain wreaking havoc.

Still, they declined to share data revealing the most recent warranty claims for such paint damages.

After an acid rainfall, moisture evaporates, leaving the acid behind.

Under the sun’s heat, the acid residue is highly concentrated to begin etching or eating through a car’s finish.

The four auto industry officials confirmed that the chemical blemish appears like a splattered raindrop, which is more conspicuous on vehicles with metallic or dark finishes.

The General motors paint development manager, Thaddeus Lasko, compared the blemish to a wet glass on a table but advised by saying;

“If it is really severe, you need to have the car refinished.”

Key Takeaways

  • How badly would it ravage your car paint if hard water blocks the piping system? Avoid it
  • Rainfall is not a free car wash. Wash and dry your vehicle immediately it stops raining
  • Polluted rainwater is a cross-border or global issue. Therefore, keep an eye on your car.








Jan-Lucas Ganssauge
Jan-Lucas Ganssauge