Brookings County, South Dakota air quality history
Daily Air Quality Index summaries from EPA monitors in Brookings, South Dakota, 1989–2025.
59%
Good days in 2025
46
Median daily AQI, 2025
5
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 Brookings, South Dakota on 365 days. 214 of those days (59%) were in the Good range, and the median daily AQI was 46. That median is higher than the typical monitored county in South Dakota (median 35.5 across 10 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 274 days. Across the years with fuller monitoring, the share of Good days rose: an average of 67% in 1999–2001 versus 71% in 2023–2025.
Years with fewer than 120 monitored days (1993, 1994, 1995, 1996, 1997, 1998…) 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)
274
75%
Ozone
85
23%
Coarse particles (PM10)
6
2%
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
214
146
4
1
0
0
46
66
154
PM2.5
2024
366
292
72
2
0
0
0
36
56
111
Ozone
2023
365
274
84
5
2
0
0
42
71
162
Ozone
2022
364
320
44
0
0
0
0
36
54
87
Ozone
2021
365
270
87
6
1
1
0
39
67
236
Ozone
2020
366
305
61
0
0
0
0
39
55
87
Ozone
2019
365
273
87
5
0
0
0
43
66
126
Ozone
2018
365
297
67
1
0
0
0
38
57
101
Ozone
2017
365
311
54
0
0
0
0
36
55
90
Ozone
2016
365
329
35
1
0
0
0
35
50
101
Ozone
2015
360
282
76
2
0
0
0
38
60
129
Ozone
2014
362
308
53
1
0
0
0
36
54
108
Ozone
2013
365
309
56
0
0
0
0
39
56
93
Ozone
2012
366
267
98
1
0
0
0
40
64
112
Ozone
2011
365
318
46
1
0
0
0
38
53
104
Ozone
2010
365
306
59
0
0
0
0
37
60
97
Ozone
2009
359
313
45
1
0
0
0
34
53
110
Ozone
2008
272
228
42
2
0
0
0
38
55
125
Ozone
2007
124
85
39
0
0
0
0
38
60
88
PM2.5
2006
131
90
41
0
0
0
0
41
60
83
PM2.5
2005
136
88
48
0
0
0
0
39
65
85
PM2.5
2004
131
79
52
0
0
0
0
41
60
90
PM2.5
2003
125
74
51
0
0
0
0
41
67
87
PM2.5
2002
132
93
39
0
0
0
0
38
62
88
PM2.5
2001
133
83
50
0
0
0
0
42
64
84
PM2.5
2000
133
95
38
0
0
0
0
36
60
92
PM2.5
1999
126
85
40
1
0
0
0
33
62
123
PM2.5
1998
116
115
1
0
0
0
0
19
39
52
PM10
1997
58
57
1
0
0
0
0
18
35
52
PM10
1996
61
58
3
0
0
0
0
18
33
62
PM10
1995
61
59
2
0
0
0
0
19
37
56
PM10
1994
60
56
4
0
0
0
0
20
41
57
PM10
1993
58
58
0
0
0
0
0
14
29
44
PM10
1992
53
53
0
0
0
0
0
19
40
49
PM10
1991
58
54
4
0
0
0
0
27
49
63
PM10
1990
58
48
9
1
0
0
0
30
58
138
PM10
1989
38
32
6
0
0
0
0
22
54
63
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 South Dakota with a similar median AQI in 2025
