Columbia County, Oregon air quality history

Daily Air Quality Index summaries from EPA monitors in Columbia, Oregon, 1980–2025.

93%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

364

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Columbia, Oregon on 364 days. 338 of those days (93%) were in the Good range, and the median daily AQI was 27. That median is about the same as the typical monitored county in Oregon (median 29 across 21 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 257 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 93% in 1981–1983 versus 93% in 2023–2025.

Years with fewer than 120 monitored days (1980, 1984) 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)	257	71%
Ozone	107	29%

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	364	338	26	0	0	0	27	45	69	PM2.5
2024	364	354	10	0	0	0	26	41	74	PM2.5
2023	365	329	34	2	0	0	29	50	115	PM2.5
2022	362	293	66	1	2	0	31	56	162	PM2.5
2021	345	319	26	0	0	0	29	47	66	PM2.5
2020	363	332	22	1	2	6	28	49	293	PM2.5
2019	363	342	21	0	0	0	27	46	84	PM2.5
2018	363	330	29	4	0	0	28	49	136	PM2.5
2017	346	306	36	2	2	0	29	52	156	PM2.5
2016	348	338	10	0	0	0	26	43	64	PM2.5
2015	359	308	50	1	0	0	33	53	120	PM2.5
2014	362	335	27	0	0	0	29	47	74	PM2.5
2013	361	296	65	0	0	0	31	57	92	PM2.5
2012	362	331	31	0	0	0	31	49	76	PM2.5
2011	361	304	57	0	0	0	29	54	79	PM2.5
2010	363	346	17	0	0	0	29	44	71	PM2.5
2009	355	293	61	1	0	0	34	54	105	PM2.5
2008	350	292	58	0	0	0	32	55	84	PM2.5
2007	357	292	65	0	0	0	32	58	96	PM2.5
2006	355	302	51	2	0	0	31	55	115	PM2.5
2005	286	235	51	0	0	0	32	55	88	PM2.5
2004	260	188	72	0	0	0	34	62	91	PM2.5
2003	172	149	22	1	0	0	31	54	108	Ozone
2002	215	192	23	0	0	0	32	51	90	Ozone
2001	218	189	29	0	0	0	32	52	93	Ozone
2000	217	187	30	0	0	0	31	54	87	Ozone
1999	288	249	39	0	0	0	29	53	97	PM2.5
1998	147	138	6	3	0	0	29	44	122	Ozone
1997	140	138	2	0	0	0	29	44	80	Ozone
1996	142	126	12	4	0	0	31	54	147	Ozone
1995	143	137	5	0	1	0	30	45	159	Ozone
1994	152	144	7	0	1	0	31	42	151	Ozone
1993	123	117	5	1	0	0	29	40	105	Ozone
1992	150	131	17	2	0	0	33	54	105	Ozone
1991	152	152	0	0	0	0	27	37	50	Ozone
1990	209	198	8	2	1	0	29	44	159	Ozone
1989	194	187	7	0	0	0	31	45	100	Ozone
1988	192	187	4	1	0	0	22	40	140	Ozone
1987	196	175	18	2	0	1	33	54	205	Ozone
1986	151	142	8	1	0	0	26	42	143	Ozone
1985	178	162	14	2	0	0	31	50	136	Ozone
1984	118	112	4	2	0	0	31	45	147	Ozone
1983	163	163	0	0	0	0	18	29	42	Ozone
1982	173	155	15	2	1	0	30	54	161	Ozone
1981	170	151	13	2	4	0	31	51	172	Ozone
1980	117	116	1	0	0	0	26	39	100	Ozone

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 Oregon with a similar median AQI in 2025

All monitored counties in Oregon

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem