Bad Air Days in Clark County, Washington: 3 a Year

3 bad air days a year

About the middle of monitored US counties. Ranked 352 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (84% particle days).

The bad-air season here

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

What to buy, and what not to

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 5 bad days a year; in 2016 to 2025, 3. Not much has changed. The worst recent year was 2020, with 9 bad days on 366 monitored days.

Date	AQI	Main pollutant
2020-09-13	874	PM2.5
2020-09-14	842	PM2.5
2020-09-12	481	PM2.5
2020-09-15	408	PM2.5
2020-09-16	353	PM2.5

An ordinary day in Clark

Across 3,652 monitored days from 2016 to 2025, the air in Clark County rated Good on 79% of them, more often than the 72% typical of monitored counties, and Moderate on 21%. The median day sat at AQI 34; one day in ten went above 60.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)69%2,511 days
ozone31%1,141 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	302	63	0	0	33	83
2024	366	321	44	1	0	31	105
2023	365	281	82	2	2	35	153
2022	365	267	93	5	3	36	175
2021	365	308	57	0	0	34	98
2020	366	272	85	9	8	32	874
2019	364	277	86	1	0	34	128
2018	365	272	87	6	0	35	135
2017	365	264	93	8	3	37	161
2016	366	304	62	0	0	31	92
2015	344	243	96	5	3	40	159
2014	365	266	94	5	0	37	133
2013	365	238	114	13	3	39	160
2012	366	263	102	1	0	37	117
2011	365	256	101	8	3	38	153
2010	365	303	62	0	0	31	90

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

Washington compared

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.