Grant County, Washington air quality history

Daily Air Quality Index summaries from EPA monitors in Grant, Washington, 2003–2025.

80%

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 Grant, Washington on 365 days. 291 of those days (80%) were in the Good range, and the median daily AQI was 28. That median is about the same as 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 78% in 2004–2006 versus 83% in 2023–2025.

Years with fewer than 120 monitored days (2003) 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	Hazardous	Median AQI	90th pct.	Max AQI	Main pollutant
2025	365	291	71	2	1	0	0	28	59	154	PM2.5
2024	366	318	48	0	0	0	0	26	53	84	PM2.5
2023	365	300	59	3	0	2	1	32	57	301	PM2.5
2022	365	279	83	0	3	0	0	30	59	165	PM2.5
2021	365	310	49	1	4	1	0	25	54	202	PM2.5
2020	366	325	31	2	4	3	1	21	52	316	PM2.5
2019	365	306	59	0	0	0	0	24	54	71	PM2.5
2018	365	289	65	4	6	1	0	26	64	273	PM2.5
2017	365	283	72	4	6	0	0	28	61	197	PM2.5
2016	361	338	23	0	0	0	0	24	45	66	PM2.5
2015	360	289	67	3	1	0	0	31	58	152	PM2.5
2014	365	303	61	1	0	0	0	27	55	118	PM2.5
2013	337	252	85	0	0	0	0	32	58	87	PM2.5
2012	365	291	74	0	0	0	0	29	56	95	PM2.5
2011	345	301	44	0	0	0	0	27	55	81	PM2.5
2010	361	317	44	0	0	0	0	27	53	82	PM2.5
2009	362	312	50	0	0	0	0	32	52	64	PM2.5
2008	365	283	82	0	0	0	0	34	57	77	PM2.5
2007	357	275	82	0	0	0	0	30	58	89	PM2.5
2006	363	281	82	0	0	0	0	33	57	89	PM2.5
2005	365	302	63	0	0	0	0	32	55	72	PM2.5
2004	363	272	89	2	0	0	0	34	58	125	PM2.5
2003	65	47	18	0	0	0	0	32	58	65	PM2.5

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 2003–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem