Daily Air Quality Index summaries from EPA monitors in Grant, Wisconsin, 1980–2025.
69%
Good days in 2025
37
Median daily AQI, 2025
3
Days above 100 in 2025
358
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Grant, Wisconsin on 358 days. 246 of those days (69%) were in the Good range, and the median daily AQI was 37. That median is about the same as the typical monitored county in Wisconsin (median 38 across 29 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 358 days. Across the years with fuller monitoring, the share of Good days fell: an average of 80% in 1980–1982 versus 65% in 2023–2025.
Years with fewer than 120 monitored days (2000, 2001, 2002, 2003, 2004, 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)
358
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
358
246
109
2
1
0
0
37
63
167
PM2.5
2024
366
263
103
0
0
0
0
36
57
82
PM2.5
2023
365
198
160
4
2
1
0
48
68
221
PM2.5
2022
359
241
118
0
0
0
0
39
58
80
PM2.5
2021
355
200
155
0
0
0
0
46
64
96
PM2.5
2020
361
235
126
0
0
0
0
40
60
84
PM2.5
2019
365
255
109
1
0
0
0
39
62
104
PM2.5
2018
351
233
118
0
0
0
0
42
61
83
PM2.5
2017
346
265
81
0
0
0
0
33
56
88
PM2.5
2016
281
205
76
0
0
0
0
38
57
81
PM2.5
2015
361
253
107
1
0
0
0
39
59
107
PM2.5
2014
361
234
126
1
0
0
0
40
62
109
PM2.5
2013
356
219
137
0
0
0
0
42
63
79
PM2.5
2012
362
219
143
0
0
0
0
43
62
93
PM2.5
2011
149
82
67
0
0
0
0
48
69
86
PM2.5
2010
120
67
52
1
0
0
0
49
70
124
PM2.5
2009
122
63
57
2
0
0
0
49
74
142
PM2.5
2008
116
39
75
2
0
0
0
56
73
143
PM2.5
2007
120
50
67
3
0
0
0
54
79
127
PM2.5
2006
128
54
73
1
0
0
0
53
71
115
PM2.5
2005
122
60
58
4
0
0
0
52
81
114
PM2.5
2004
114
57
55
2
0
0
0
52
69
124
PM2.5
2003
119
57
60
2
0
0
0
52
72
112
PM2.5
2002
116
56
60
0
0
0
0
52
71
85
PM2.5
2001
107
47
59
1
0
0
0
52
78
119
PM2.5
2000
51
28
22
1
0
0
0
48
81
113
PM2.5
1999
57
20
35
2
0
0
0
58
76
115
PM2.5
1984
167
125
31
10
1
0
0
43
90
161
Ozone
1983
181
114
48
14
5
0
0
43
101
177
Ozone
1982
176
133
36
7
0
0
0
40
77
115
Ozone
1981
221
170
40
9
2
0
0
37
84
169
Ozone
1980
333
296
29
8
0
0
0
31
54
150
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 Wisconsin with a similar median AQI in 2025
