Grays Harbor County, Washington air quality history

Daily Air Quality Index summaries from EPA monitors in Grays Harbor, Washington, 1990–2025.

97%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

365

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Grays Harbor, Washington on 365 days. 355 of those days (97%) were in the Good range, and the median daily AQI was 22. That median is lower than the typical monitored county in Washington (median 28 across 30 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 365 days. Across the years with fuller monitoring, the share of Good days rose: an average of 69% in 2002–2004 versus 96% in 2023–2025.

Years with fewer than 120 monitored days (1990, 1991, 1992, 1993, 1994, 1995) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Fine particles (PM2.5)	365	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Very Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2025	365	355	10	0	0	0	22	41	76	PM2.5
2024	366	353	13	0	0	0	20	36	64	PM2.5
2023	365	339	26	0	0	0	23	43	80	PM2.5
2022	365	340	24	1	0	0	22	43	112	PM2.5
2021	365	347	18	0	0	0	26	42	82	PM2.5
2020	366	330	28	1	2	5	27	50	242	PM2.5
2019	352	327	25	0	0	0	27	47	62	PM2.5
2018	365	324	37	1	3	0	29	51	168	PM2.5
2017	365	313	49	2	1	0	27	53	162	PM2.5
2016	364	330	34	0	0	0	28	49	75	PM2.5
2015	343	303	40	0	0	0	29	51	68	PM2.5
2014	365	319	46	0	0	0	27	52	71	PM2.5
2013	365	276	89	0	0	0	28	59	75	PM2.5
2012	366	319	47	0	0	0	27	53	83	PM2.5
2011	363	331	32	0	0	0	21	47	64	PM2.5
2010	365	355	10	0	0	0	22	38	76	PM2.5
2009	365	275	90	0	0	0	37	58	85	PM2.5
2008	366	266	100	0	0	0	38	56	85	PM2.5
2007	362	271	91	0	0	0	32	60	83	PM2.5
2006	365	318	47	0	0	0	24	52	84	PM2.5
2005	365	320	45	0	0	0	29	52	65	PM2.5
2004	366	268	98	0	0	0	37	58	87	PM2.5
2003	365	263	102	0	0	0	39	58	83	PM2.5
2002	131	79	52	0	0	0	43	66	84	PM2.5
1995	6	6	0	0	0	0	17	26	26	PM10
1994	61	61	0	0	0	0	18	29	34	PM10
1993	60	60	0	0	0	0	18	36	44	PM10
1992	56	56	0	0	0	0	24	35	47	PM10
1991	28	28	0	0	0	0	18	25	46	PM10
1990	45	45	0	0	0	0	17	23	46	PM10

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Washington with a similar median AQI in 2025

All monitored counties in Washington

Source: U.S. EPA AirData, “Annual AQI by County” files for 1990–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem