Daily Air Quality Index summaries from EPA monitors in Crook, Oregon, 1980–2025.
73%
Good days in 2025
28
Median daily AQI, 2025
2
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 Crook, Oregon on 365 days. 266 of those days (73%) were in the Good range, and the median daily AQI was 28. 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 365 days. Across the years with fuller monitoring, the share of Good days fell: an average of 96% in 1980–1982 versus 74% in 2023–2025.
Years with fewer than 120 monitored days (2008) 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)
365
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
365
266
97
2
0
0
0
28
65
144
PM2.5
2024
366
282
76
5
3
0
0
24
64
173
PM2.5
2023
365
267
86
6
6
0
0
33
63
171
PM2.5
2022
359
288
69
2
0
0
0
24
58
128
PM2.5
2021
365
281
75
6
3
0
0
28
62
190
PM2.5
2020
365
261
97
0
1
3
3
28
65
1033
PM2.5
2019
365
266
98
1
0
0
0
30
63
103
PM2.5
2018
363
251
105
5
2
0
0
34
70
169
PM2.5
2017
357
229
112
8
7
1
0
35
78
224
PM2.5
2016
348
261
86
1
0
0
0
26
62
115
PM2.5
2015
362
252
102
6
2
0
0
32
68
170
PM2.5
2014
365
250
105
4
6
0
0
31
76
180
PM2.5
2013
365
198
154
11
2
0
0
47
82
151
PM2.5
2012
360
239
119
2
0
0
0
33
66
105
PM2.5
2011
356
241
109
6
0
0
0
28
73
143
PM2.5
2010
359
278
80
1
0
0
0
27
61
102
PM2.5
2009
365
228
132
5
0
0
0
36
71
131
PM2.5
2008
49
7
37
4
1
0
0
77
103
156
PM2.5
1983
304
299
5
0
0
0
0
35
44
58
Ozone
1982
321
310
11
0
0
0
0
33
46
64
Ozone
1981
314
310
4
0
0
0
0
32
42
61
Ozone
1980
321
293
27
1
0
0
0
40
50
126
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
