What do Seattle rain, cedar pollen, wildfire ash and road grime do to paint?
Short answer
Each one leaves something behind that sticks to paint and slowly dulls it. Rain mixes with road film into a grimy layer, cedar pollen and sap cling and stain, and winter road grime is harsh. Wildfire ash is gritty when dry and becomes a caustic slurry when damp, so rinse it with plenty of water and wash the car the same day. A coating helps these contaminants rinse off more easily, but regular washing is still what protects the paint.
Quick facts
| Year-round | Rain and road film |
|---|---|
| Spring | Cedar pollen |
| Fire season | Ash scratches when dry and becomes caustic when damp |
| Under trees | Sap and bird droppings |
| Winter | Road grime |
Isn't rain basically a free car wash?
Not really. Rain picks up oily road film thrown up by other cars and leaves it behind as it dries. That film builds up into a dull, gritty layer.
What does cedar pollen do?
In spring, pollen coats cars in a yellow-green dust. Mixed with rain, it turns sticky and can stain if it sits. Rinse it off promptly.
What about wildfire ash?
Ash is gritty, so wiping it off dry scratches the paint. When ash gets wet from rain, morning dew or even humidity, it turns into a caustic slurry that can etch the clear coat. Repeated wet and dry cycles can bake it on. Don't wipe it dry and don't let it sit damp. Rinse it off with plenty of water and wash the car the same day.
Why remove sap and bird droppings quickly?
They're sticky or acidic, and they do more harm the longer they sit. Bird droppings, sap and pollen should all come off quickly, even between regular washes.
What does a coating change?
A coating gives grime less to grip, so it rinses off faster and washing is easier. It doesn't replace washing. See how to wash a ceramic coated car.
How APC Auto Spa does it
APC Auto Spa has worked on cars in western Washington since 2015, at shops in Tukwila and Monroe. Annual maintenance includes a decontamination wash that clears out a year of buildup.
Frequently asked questions
- How often should I wash my car in Seattle?
- Every two weeks if possible, monthly at a minimum, and spot-clean droppings, sap and pollen as soon as you see them.
- Should I dry-wipe pollen or ash off?
- No. Rinse it off with plenty of water so the grit doesn't scratch the paint. With ash, wash it off the same day because wet ash becomes caustic.
- Does a coating make my car stay clean in the rain?
- It helps dirt release more easily, but the car will still get dirty. It just cleans up faster.
Reviewed by Heather Humphrey, co-owner of APC Auto Spa ยท Last updated October 2026
Heather leads customer education and training at APC's Tukwila and Monroe shops.