Daily Air Quality Index summaries from EPA monitors in Stearns, Minnesota, 1985–2025.
76%
Good days in 2025
37
Median daily AQI, 2025
11
Days above 100 in 2025
357
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Stearns, Minnesota on 357 days. 270 of those days (76%) were in the Good range, and the median daily AQI was 37. That median is about the same as the typical monitored county in Minnesota (median 37 across 21 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 204 days. Across the years with fuller monitoring, the share of Good days fell: an average of 92% in 1987–1989 versus 69% in 2023–2025.
Years with fewer than 120 monitored days (1985, 1986, 1992) 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)
204
57%
Ozone
153
43%
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
357
270
76
8
3
0
0
37
62
165
PM2.5
2024
366
282
84
0
0
0
0
39
58
97
PM2.5
2023
365
199
152
11
3
0
0
48
83
184
PM2.5
2022
277
204
73
0
0
0
0
39
58
78
PM2.5
2021
362
261
95
3
2
1
0
40
68
252
PM2.5
2020
366
309
57
0
0
0
0
36
53
80
PM2.5
2019
344
290
54
0
0
0
0
34
55
94
Ozone
2018
365
283
81
1
0
0
0
38
61
101
PM2.5
2017
365
294
71
0
0
0
0
37
55
87
PM2.5
2016
366
318
48
0
0
0
0
33
52
97
PM2.5
2015
355
306
48
0
1
0
0
37
53
151
PM2.5
2014
358
285
73
0
0
0
0
37
58
89
PM2.5
2013
359
273
86
0
0
0
0
39
60
85
PM2.5
2012
366
239
126
1
0
0
0
43
61
105
PM2.5
2011
355
225
128
2
0
0
0
42
65
101
PM2.5
2010
359
244
113
2
0
0
0
40
60
120
PM2.5
2009
365
263
100
2
0
0
0
42
65
110
PM2.5
2008
366
242
121
2
1
0
0
43
65
152
PM2.5
2007
365
267
92
6
0
0
0
39
63
148
PM2.5
2006
365
267
98
0
0
0
0
38
60
87
PM2.5
2005
365
240
122
2
1
0
0
42
66
154
PM2.5
2004
366
245
117
4
0
0
0
38
66
135
PM2.5
2003
365
209
154
2
0
0
0
46
73
113
PM2.5
2002
360
317
42
1
0
0
0
13
53
112
CO
2001
351
301
50
0
0
0
0
13
57
84
CO
2000
325
285
37
3
0
0
0
16
54
113
CO
1999
365
365
0
0
0
0
0
15
25
38
CO
1998
355
355
0
0
0
0
0
17
28
44
CO
1997
351
351
0
0
0
0
0
18
30
45
CO
1996
366
366
0
0
0
0
0
19
33
47
CO
1995
356
354
2
0
0
0
0
24
38
63
CO
1994
362
346
16
0
0
0
0
27
42
85
CO
1993
350
340
10
0
0
0
0
25
40
57
CO
1992
57
57
0
0
0
0
0
25
41
50
CO
1990
318
303
15
0
0
0
0
24
38
89
CO
1989
365
344
21
0
0
0
0
23
42
92
CO
1988
253
241
12
0
0
0
0
26
41
77
CO
1987
129
111
16
2
0
0
0
30
56
133
CO
1986
114
108
6
0
0
0
0
23
44
70
PM10
1985
98
91
7
0
0
0
0
21
44
68
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 Minnesota with a similar median AQI in 2025
