The first rain of the season is worse for your paint than no rain at all

The first storm gets forecast about a week out, and the same message comes in every year: should I bother washing it, it is going to rain anyway.

Rain does not wash a car. It develops what is already on it.

What is sitting on your paint right now

Nothing has properly rinsed the Valley since spring. Every panel has been collecting brake dust off the 101 and the 405, tire rubber, diesel soot, pollen, sprinkler minerals and the grit the Santa Anas have been pushing through the passes all month. On a car that sleeps outside in Northridge or Simi Valley, that is a layer you can write your name in.

A raindrop does not rinse that away. It lands on the dust, wets a patch of it, then the sun comes back and the water leaves. The dirt does not. An even grey film turns into thousands of hard rings with the grime concentrated at the edge of each one. That is the spotting people see on a dark car two days after a storm and blame on the rain.

Why the first one is the worst one

Rain picks up whatever it falls through, and after six months of dry weather there is plenty in the air over the basin. The first storm is the dirty one. By January, after a few real soakings have scrubbed the air out, the rain landing on your hood is much closer to clean water. The first one leaves the marks.

Then the heat comes straight back, because this is still October. A wet, dirt heavy deposit baking on a black roof in afternoon sun is how clear coat gets etched, and etching is not dirt. It is a mark in the surface of the paint, and no wash takes it out.

The roads add their own layer

Oil and rubber build up in the road surface over a dry summer, and the first rain floats all of it to the top before there is enough water running to carry it away. Anyone who has driven the 405 through the Sepulveda Pass or the 118 on a first wet morning knows how greasy it feels.

Your car wears some of it. Spray off the truck in front puts a brown film down the lower doors and rocker panels, and it carries tar specks that set hard once the panel dries. Those still look like dirt but will not come off with soap, and they are what a clay bar pulls out of the paint in November.

Do not reach for the wipers

The first drops hit a dusty windshield and the instinct is to run the blades. They drag mineral grit in an arc across the glass, and those arcs do not polish out. Soak it with washer fluid first, or get the dust off the glass before the weather arrives.

What to do before a storm

If rain is a couple of days out, that is the best time to wash, not the worst. A clean, waxed panel makes water bead up and run off, and it takes the dirt with it. A flat, dusty panel holds the water in a sheet until it dries in place. A Pristine Exterior two days before a storm saves you the mess afterwards, which is the opposite of what people assume.

If the car has sat through the whole of Santa Ana season untouched, the better call is the Platinum Exterior. The clay bar lifts out the grit that has already bonded into the clear coat, the trim restore does the plastic the sun has gone grey, and the sealant gives the rest of the wet season something slick to land on. What a windy week does to your paint covers why that grit is there in the first place.

What to do after one

Get it washed within a few days, while the deposits are still on top of the clear coat rather than into it. Rinse before anything touches the paint, then foam, two buckets, and dry it with a towel instead of letting hard Valley water dry on its own and spot it again.

Do not wipe it down dry because it looks nearly clean. There is grit in that film, and a dry towel turns it into swirl marks.

The inside is the part people forget

Wet shoes and a wet dog put more water into a car than the storm does. Rubber mats hold a puddle underneath them, and carpet stays damp for weeks when the car is shut and parked in shade. That damp is where the December musty smell comes from, and by then it is in the padding rather than the surface, so airing it out does nothing. Pull the mats out and dry them. If the carpet already smells, it needs the steam and shampoo in a Platinum Interior rather than a vacuum.

One more worth five minutes of your own time: clear the wet leaves out of the cowl at the base of the windshield and off the sunroof seal. Those drains block with sycamore and liquidambar leaf mush, water backs up, and it ends up in the carpet or the headliner. That is a bigger repair than any detail.

The rest of the wet season

Wash more often than you think, and seal it once. Between storms a car gets dirtier here than it does in summer, because everything the road throws up is wet when it lands. The realistic schedule is in how often to detail a car in Los Angeles.

We come to you, so your driveway is the shop. We cover the San Fernando Valley, the Conejo Valley and Ventura County. Book online and we call or text to confirm.