In an ideal situation you would never usually attempt to wash your car in hot weather or direct sunlight for various different reasons, the main one being that the shampoo residue and rinse water can quickly dry onto the surface of the paintwork resulting in unsightly water spotting, streaking and drip marks which can often be difficult to remove and which can actually damage the paintwork in some instances. It is not however, always possible to wash your car in complete shade or cool conditions only, especially if you live in a particularly sunny or hot climate and so washing you car in the heat can often be unavoidable.
If this is the case then you do not necessarily have to battle against the heat whilst trying to safely and properly wash your car as there are a number of things that can be done and precautions that can be taken to minimize the amount of water drying onto the surface and reduce the potential of damage being done.
The most sensible thing to do if you have to wash your car in direct sunlight or a hot climate is to wash it earlier in the morning before the heat of the sun begins to really set in, or later on in the evening when temperatures have dropped and the sun is at a lower level in the sky. As with washing in the shade however, this too may not be possible due to time constrains or noise issues etc and so if you are forced to wash during the heat of the day then the most important thing you can do is make sure you choose a suitable shampoo product.
There are some shampoo products that are far more suitable for using in the heat and direct sunlight. You should pick a car wash product that has a mild, gentle, PH neutral and wax friendly formula that contains only high quality ingredients, which are preferably natural, at least in part. It is important that you do your research and find an appropriate product as the use of an inferior or strong product will considerably increase the likely hood of stubborn residue marks being inflicted.
Depending on the area you live in, hard water can be issue and can contribute greatly to water spotting and streaking when washing in the heat. Deposits and contaminants in the water dry and bond onto the surface after the actual water has evaporated and it is these deposits that cause such unsightly and awkward to remove marks in the finish of your paintwork. There are specialist filtration units available that can eliminate the deposits and purify the water which means that you can actually wash in direct sunlight and not be left with any water spotting whatsoever even if the car is not dried!
This really is the ideal solution to washing in the heat, however such units can be fairly costly and can add considerable time and effort to the car washing process, so for now, we will assume that you are not using a water filtration system and are washing using whatever quality of water you are being provided with and will concentrate on the other things that can be done to minimize any water spotting and damage being inflicted.
When washing in the heat one of the best things to do prior to wetting the car is to ensure that you have all the equipment and products you need set up and close at hand. Your wash buckets should be filled with shampoo, the hose pipe or pressure washer should be connected and turned on and you should ensure you have enough length in the hose to comfortably reach around the car fully, and then any other tools and brushes etc should be taken out placed nearby. Doing this will reduce the chance of water drying onto the surface as you will have to spend less time moving around and fiddling about during washing. Before cleaning the body, just as when washing in any other conditions, the wheels should be washed and rinsed first as this will help to reduce any time water is left sitting on the body of the vehicle.
Unlike washing in a cool environment however, the whole car should not be washed in one single step. Instead, you should wash and rinse a panel at a time beginning at the top of the vehicle and working your way down, ensuring that you also rinse the panel first to initially help reduce the surface temperature and ensure it is wet and well lubricated for the contact washing.
Although you should never rush when washing your car, you may want to work with a little more haste than you would in cool conditions and more than anything ensure you work in a methodical and efficient manner. After all panels have been sufficiently washed and rinsed separately, you should give the whole car a final thorough rinse down to ensure any remaining suds and shampoo residues are fully removed and that all areas are wet before drying. You should then quickly move onto drying with a suitable microfiber towel.
A detailing spray or drying aid should ideally be applied to the wet car before actually toweling it dry as this will further help to reduce water spotting and streaking. When drying you should pay particular attention to areas where water collects like the wing mirrors, badges and trim, as it is this collected water that can then drip out onto the hot paintwork and cause unsightly, stubborn drip marks after the rest of the car has been dried. The door shuts should also be dried off to remove any standing water and also the opening and closing of the doors will help to fully release any further trapped water which can then be blotted up at the end of the drying process.
It is important to note here that if your vehicle has been previously properly polished and waxed or sealed then it will be much easier to wash – reducing the amount of time it takes in the heat, and a properly prepared surface will reduce the amount of standing water on it after rinsing and so reduce the amount of potential water spotting, plus any water spotting should be easily removed because the deposits will not be able to bond to the paintwork as they will instead be sitting on the protective wax or sealant layer. It is therefore definitely worthwhile considering doing this if you are likely to have to wash your car in direct sunlight or heat on a regular basis.
One final thing to consider is the use of a waterless car wash product or high quality detailing spray to maintain your car after an initial thorough wash and prevent it from becoming too contaminated again so that washing with water and shampoo in the heat doesn’t actually have to be undertaken. This will eliminate the possibility of the surface being damaged by water marks but it needs to be done on a regular basis and only on your car when it is not yet heavily contaminated, in order to prevent any damage in the form of light scratches or swirl marks being inflicted.