Daily Air Quality Index summaries from EPA monitors in Prowers, Colorado, 1985–2025.
93%
Good days in 2025
27
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 Prowers, Colorado on 365 days. 338 of those days (93%) were in the Good range, and the median daily AQI was 27. That median is lower than the typical monitored county in Colorado (median 46 across 27 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 294 days. Across the years with fuller monitoring, the share of Good days rose: an average of 87% in 1985–1988 versus 92% in 2023–2025.
Years with fewer than 120 monitored days (1987, 1989, 1990, 1991) 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)
294
81%
Coarse particles (PM10)
71
19%
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
338
25
0
0
1
1
27
45
652
PM2.5
2024
366
321
45
0
0
0
0
25
52
98
PM2.5
2023
350
336
13
1
0
0
0
19
40
103
PM10
2022
354
330
22
0
1
0
1
18
41
330
PM10
2021
361
345
14
1
0
0
1
19
39
584
PM10
2020
350
327
19
1
2
1
0
17
42
238
PM10
2019
346
343
3
0
0
0
0
14
28
76
PM10
2018
359
353
5
1
0
0
0
16
31
103
PM10
2017
353
347
6
0
0
0
0
17
37
67
PM10
2016
357
350
6
1
0
0
0
17
34
115
PM10
2015
351
339
9
1
0
2
0
14
34
299
PM10
2014
358
330
19
2
6
1
0
19
43
247
PM10
2013
361
324
30
5
0
1
1
18
51
1185
PM10
2012
366
342
20
4
0
0
0
23
44
144
PM10
2011
365
344
19
2
0
0
0
21
43
119
PM10
2010
365
341
24
0
0
0
0
24
44
91
PM10
2009
365
345
16
4
0
0
0
22
42
140
PM10
2008
365
338
25
1
0
1
0
23
46
218
PM10
2007
363
344
19
0
0
0
0
22
42
70
PM10
2006
365
351
14
0
0
0
0
19
35
91
PM10
2005
364
357
6
1
0
0
0
19
32
125
PM10
2004
365
347
18
0
0
0
0
20
40
70
PM10
2003
363
338
25
0
0
0
0
24
46
89
PM10
2002
365
316
45
4
0
0
0
24
53
146
PM10
2001
364
324
40
0
0
0
0
23
51
99
PM10
2000
357
323
33
1
0
0
0
23
49
112
PM10
1999
365
334
30
1
0
0
0
24
47
125
PM10
1998
361
335
26
0
0
0
0
22
46
92
PM10
1997
349
333
16
0
0
0
0
18
41
78
PM10
1996
358
345
12
0
1
0
0
19
40
153
PM10
1995
337
314
21
2
0
0
0
20
45
113
PM10
1994
357
343
14
0
0
0
0
19
40
94
PM10
1993
361
354
7
0
0
0
0
20
34
62
PM10
1992
336
304
31
1
0
0
0
23
50
104
PM10
1991
53
48
4
0
1
0
0
21
48
185
PM10
1990
57
57
0
0
0
0
0
17
32
43
PM10
1989
49
46
3
0
0
0
0
21
43
62
PM10
1988
121
115
6
0
0
0
0
22
37
74
PM10
1987
106
105
1
0
0
0
0
23
36
54
PM10
1986
253
212
39
1
0
0
1
29
56
307
PM10
1985
175
144
30
1
0
0
0
28
57
104
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 Colorado with a similar median AQI in 2025
