Daily Air Quality Index summaries from EPA monitors in Clark, Washington, 1980–2025.
83%
Good days in 2025
33
Median daily AQI, 2025
0
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 Clark, Washington on 365 days. 302 of those days (83%) were in the Good range, and the median daily AQI was 33. That median is higher 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 241 days. Across the years with fuller monitoring, the share of Good days fell: an average of 85% in 1980–1982 versus 82% in 2023–2025.
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)
241
66%
Ozone
124
34%
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
302
63
0
0
0
0
33
56
83
PM2.5
2024
366
321
44
1
0
0
0
31
53
105
PM2.5
2023
365
281
82
0
2
0
0
35
59
153
PM2.5
2022
365
267
93
2
3
0
0
36
66
175
PM2.5
2021
365
308
57
0
0
0
0
34
55
98
PM2.5
2020
366
272
85
1
0
3
5
32
62
874
PM2.5
2019
364
277
86
1
0
0
0
34
63
128
PM2.5
2018
365
272
87
6
0
0
0
35
59
135
PM2.5
2017
365
264
93
5
3
0
0
37
71
161
PM2.5
2016
366
304
62
0
0
0
0
31
56
92
PM2.5
2015
344
243
96
2
3
0
0
40
65
159
PM2.5
2014
365
266
94
5
0
0
0
37
63
133
PM2.5
2013
365
238
114
10
3
0
0
39
72
160
PM2.5
2012
366
263
102
1
0
0
0
37
63
117
PM2.5
2011
365
256
101
5
3
0
0
38
73
153
PM2.5
2010
365
303
62
0
0
0
0
31
57
90
PM2.5
2009
365
199
157
8
1
0
0
46
75
151
PM2.5
2008
366
250
112
4
0
0
0
40
70
108
PM2.5
2007
364
246
108
10
0
0
0
40
71
145
PM2.5
2006
363
247
113
3
0
0
0
38
66
115
PM2.5
2005
365
257
106
1
1
0
0
39
64
158
PM2.5
2004
366
254
109
3
0
0
0
38
63
125
PM2.5
2003
365
227
134
4
0
0
0
43
67
119
PM2.5
2002
363
232
126
4
1
0
0
43
62
152
PM2.5
2001
365
228
134
3
0
0
0
43
63
126
PM2.5
2000
366
284
76
6
0
0
0
34
60
134
PM2.5
1999
365
311
51
3
0
0
0
30
55
111
CO
1998
365
338
24
3
0
0
0
31
46
140
CO
1997
365
329
36
0
0
0
0
34
50
93
CO
1996
366
326
33
4
3
0
0
34
53
179
CO
1995
365
329
34
0
2
0
0
33
50
169
CO
1994
363
323
36
3
0
1
0
34
52
206
CO
1993
361
328
32
1
0
0
0
33
50
126
CO
1992
357
307
49
0
1
0
0
31
56
179
CO
1991
355
274
75
5
1
0
0
36
67
153
CO
1990
355
283
66
3
3
0
0
32
66
200
CO
1989
358
283
73
2
0
0
0
34
67
106
CO
1988
340
271
62
7
0
0
0
34
61
126
CO
1987
318
246
65
5
2
0
0
28
69
159
CO
1986
278
257
18
2
1
0
0
29
44
154
Ozone
1985
359
331
23
5
0
0
0
31
48
122
Ozone
1984
362
336
24
1
1
0
0
28
45
161
CO
1983
365
322
41
2
0
0
0
30
54
115
CO
1982
365
306
57
1
1
0
0
35
58
156
CO
1981
363
309
50
3
1
0
0
33
60
151
CO
1980
365
317
46
0
2
0
0
32
55
165
CO
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
