Bad Air Days in Columbia County, Oregon: 2 a Year

2 bad air days a year

About the middle of monitored US counties. Ranked 465 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (91% particle days).

Which months to watch

Most bad days here fall in September and August and October. Averaged over 2016 to 2025.

What actually helps here

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

The worst days on file

In 2000 to 2009 this county averaged under 1 bad days a year; in 2016 to 2025, 2. Not much has changed. The worst recent year was 2020, with 9 bad days on 363 monitored days.

Date	AQI	Main pollutant
2020-09-13	293	PM2.5
2020-09-14	291	PM2.5
2020-09-12	276	PM2.5
2020-09-15	255	PM2.5
2020-09-16	224	PM2.5

Most days, not the worst ones

Across 3,583 monitored days from 2016 to 2025, the air in Columbia County rated Good on 92% of them, more often than the 72% typical of monitored counties, and Moderate on 8%. The median day sat at AQI 28; one day in ten went above 48.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)68%2,433 days
ozone32%1,150 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	364	338	26	0	0	27	69
2024	364	354	10	0	0	26	74
2023	365	329	34	2	0	29	115
2022	362	293	66	3	2	31	162
2021	345	319	26	0	0	29	66
2020	363	332	22	9	8	28	293
2019	363	342	21	0	0	27	84
2018	363	330	29	4	0	28	136
2017	346	306	36	4	2	29	156
2016	348	338	10	0	0	26	64
2015	359	308	50	1	0	33	120
2014	362	335	27	0	0	29	74
2013	361	296	65	0	0	31	92
2012	362	331	31	0	0	31	76
2011	361	304	57	0	0	29	79
2010	363	346	17	0	0	29	71

*2025 may be a partial year in EPA's file.

Nearby counties on file

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day.