Daily Air Quality Index summaries from EPA monitors in Okanogan, Washington, 1987–2025.
57%
Good days in 2025
41
Median daily AQI, 2025
4
Days above 100 in 2025
361
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Okanogan, Washington on 361 days. 204 of those days (57%) were in the Good range, and the median daily AQI was 41. That median is higher than the typical monitored county in Washington (median 28 across 30 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 361 days. Across the years with fuller monitoring, the share of Good days fell: an average of 65% in 1988–2003 versus 56% in 2023–2025.
Years with fewer than 120 monitored days (1987, 2001) 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)
361
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
361
204
153
3
1
0
0
41
67
160
PM2.5
2024
366
225
140
1
0
0
0
38
65
102
PM2.5
2023
365
185
171
2
5
2
0
49
73
299
PM2.5
2022
365
175
185
4
0
1
0
52
73
248
PM2.5
2021
365
146
193
5
8
11
2
54
86
354
PM2.5
2020
366
196
157
1
6
2
4
47
74
618
PM2.5
2019
365
209
156
0
0
0
0
42
68
91
PM2.5
2018
365
174
158
9
20
2
2
52
81
372
PM2.5
2017
365
167
181
2
13
2
0
52
81
242
PM2.5
2016
366
222
142
2
0
0
0
38
71
118
PM2.5
2015
363
173
173
6
4
1
6
52
76
820
PM2.5
2014
356
197
150
7
2
0
0
44
78
155
PM2.5
2013
365
196
163
6
0
0
0
46
72
131
PM2.5
2012
366
197
159
5
5
0
0
47
71
161
PM2.5
2011
364
219
144
1
0
0
0
38
69
104
PM2.5
2010
365
223
142
0
0
0
0
38
68
94
PM2.5
2009
364
200
164
0
0
0
0
44
66
85
PM2.5
2008
365
214
151
0
0
0
0
41
70
88
PM2.5
2007
364
181
183
0
0
0
0
51
73
97
PM2.5
2006
362
177
155
21
9
0
0
51
89
188
PM2.5
2005
365
232
133
0
0
0
0
37
64
93
PM2.5
2004
366
175
187
4
0
0
0
52
73
125
PM2.5
2003
362
142
214
6
0
0
0
55
82
133
PM2.5
2002
157
97
56
4
0
0
0
23
88
113
PM2.5
2001
108
103
5
0
0
0
0
11
31
61
PM2.5
1988
122
116
6
0
0
0
0
26
43
64
PM10
1987
58
44
14
0
0
0
0
38
58
69
PM10
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
