29 November 2023

Should you wash your car when it is raining?

When it comes to washing your car, the jury is out when it comes to whether or not you should do it when it is raining. For some, they believe that the rain provides a helping hand when it comes to rinsing off the shampoo from your car. For others, they believe that the potential for acid rain damage or pollutants in the rain can cause potential damage to your vehicle.

We tend to lean more towards the side of washing your car in the rain is absolutely fine, especially for us down here in New Zealand. For our customers in other countries like the USA or the UK, it might be different depending on where you live and we have outlined some of the potential drawbacks below, however, in the main, washing your car in the rain should be absolutely fine.

Another related question is whether you can use rainwater collected from your roof to wash your car and once again, the answer from us is an overwhelming yes and we have gone into more detail about this below.

Why you should wash your car in the rain

For most people, no matter where you live, you will be perfectly fine washing your car in the rain and in fact, there are some benefits to washing your car in the rain.

In hot weather like we see here in New Zealand, washing your car can be tricky and we would never advise that you wash your car in the heat of the day. Heat and direct sunlight can cause shampoo residue and the water you use to rinse your car to dry onto the surface of the paint resulting in unsightly water spotting, streaking and drip marks. These can be tricky to remove and over time, can actually cause damage to your paintwork.

Washing your car in the rain will ensure no such issues, although sometimes it can be harder to find a rainy day in the middle of summer in particularly hot destinations.

Benefits of washing your car in the rain

As well as the obvious issues you avoid of not washing your car in the sunshine and heat, washing your car in the rain also has some other benefits that make it more appealing:

1.      It is a natural pre-rinse

For those who take their car washing seriously, pre-rinsing your car is an important step in the cleaning process. It helps to remove any dust and loose impediments and also creates a slick surface for you to apply your shampoo. This helps to reduce swirl marks in the long run and is an important step in the car washing process.

The rain will pre-rinse your car for you and because rainwater is naturally soft, this is a great way to pre-rinse your car with water that is free from minerals and less likely to leave spots.

Having a car that is pre-rinsed before you wash it also helps to save water as you will not need to use water from the mains or from your water tank to carry out a pre-rinse.

2.      It reduces the chance of water spotting

Water spotting is one of the main issues that can develop after you wash your car, especially in hot climates where the products you use to clean your car along with the water you use to rinse can dry too quickly and lead to spotting.

Washing your car in the rain will ensure that the products you use are washed off almost as you go, ensuring they never get the opportunity to dry on your vehicle. This will greatly reduce the potential for water spotting and may actually eliminate it altogether.

3.      It helps to wash off the shampoo

One of the biggest challenges, when you wash your car in dry weather, is ensuring you don’t allow the shampoo to dry and streak. This sometimes means washing one side of your car and rinsing it off before it has the chance to dry.

When you wash your car in the rain, you get a helping hand with this. As you work your way around your car, the rain will wash away the shampoo as you go and whilst it may not get rid of all the shampoo, it will certainly go a long way towards ensuring you don’t end up with a streaky-looking car.

Similar to pre-rinsing, this will also save you water which could be especially beneficial in dry climates or if you use tank water at home where every drop is precious. It also saves you time as you won’t need to spend as much time rinsing your car after you have shampooed it.

Drawbacks of washing your car in the rain

There are some people that say you shouldn’t wash your car in the rain. Here are some of the reasons suggested:

1.      Acid rain

If you live in a heavily polluted part of the world, where there is lots of smog and pollution, acid rain is something that you might be familiar with. This is not specific to washing your vehicle in the rain and if you do live in such an area, there is a chance your paintwork could be damaged over time if it is subjected to acidic rain on a regular basis.

The problem with washing your car in areas where acid rain is prevalent is that the acid rain will often dry on your vehicle and wetting it reactivates it, potentially causing further damage.

For most people reading this post, this will not be an issue to worry about and if you do live in an area with regular acid rainfall, you will already be aware of this issue.

2.      Muddy puddles

If you wash your car at home in the rain and it then sits on the driveway, this is less of an issue, however, if you choose to head to the car wash when it is raining, then muddle puddles and surface water could be an issue.

As your drive home in your newly cleaned car, there is a good chance you will get surface spray splashing up onto your vehicle, certainly on the underside and under your wheel arches. This could make your car dirty again almost as soon as your drive out of the car wash.

The road is full of all sorts of dirt, debris, salt, oil and other contaminants and once it is wet, these are sprayed up onto your vehicle, defeating the object of cleaning it in the first place.

This is a definite drawback if you have to drive your vehicle somewhere to wash it. If you are simply washing your car on your own driveway and waiting until the road dries, you will be absolutely fine to wash your car in the rain.

3.      People think you are mad!

If you get out there and wash your car in the rain, your neighbours might think you have gone mad! This is especially true if you take the advice of some people when washing your car in the rain and put on your swimsuit!

A swimsuit is a practical piece of clothing in which to wash the car in the rain seeing as it is designed to get wet. It also means you don’t end up getting your favourite clothes soaking wet as you clean the car.

If you are not bothered if the neighbours think you are a little bit mad, we recommend getting out there in the rain and washing your car in your swimsuit – it’s a liberating experience!

Is rainwater collected in a tank good for washing cars?

Another related question we often see being asked is whether or not the rainwater you collect from your roof and store in a water tank is good for washing cars.

Many people install a water tank for the purpose of carrying out outdoor chores like watering the garden and washing the car. It’s therefore good to know whether or not the water you collect is safe to use when washing your car.

For most people, the rainwater you collect in your tank will be even better than the rainwater that falls straight from the sky. That’s because of the filtration systems in place as the water is diverted from your roof into your tank.

If you are only using your collected rainwater for non-potable reasons, you might not have as many filtration systems in place as you would if you were collecting that rainwater for drinking, cooking and bathing, however, you will still have systems in place to stop as much debris as possible from entering your tank.

This helps to filter out microparticles that have been picked up as the rain falls from the sky, helping to ensure that the water you collect is clean and perfectly safe for washing your car.

We often get asked the same question when it comes to laundry and whether or not rainwater is clean for laundry. The simple answer to that one is also a resounding yes in most places in the world. You can read our blog about rainwater and laundry and learn more.

Collecting rainwater in New Zealand

Rainwater is a great way to supplement your mains water supply here in New Zealand, or for many properties, it is the main source of water to a property.

Washing your car with rainwater is a great way to conserve water and cut down on your monthly bills. If you are someone that takes great pride in their car and likes to wash it on a regular basis, collecting rainwater for washing your car can be a great way to save money in the long run, especially when that water can be used for other tasks like watering the garden or washing the windows.

You can read more about the basics of collecting rainwater here in New Zealand in our beginner’s guide to collecting and using rainwater. Here you will find handy tips on selecting the best rainwater tank for your needs as well as the process of filtering and connecting your rainwater tank to your property. You can also find out more information about Smart Water’s range of rainwater tank indicators – helping you to keep on top of your water usage and ensure you are maximising the rainwater you collect.