Daily Air Quality Index summaries from EPA monitors in Milwaukee, Wisconsin, 1980–2025.
62%
Good days in 2025
43
Median daily AQI, 2025
16
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 Milwaukee, Wisconsin on 365 days. 228 of those days (62%) were in the Good range, and the median daily AQI was 43. That median is higher than the typical monitored county in Wisconsin (median 38 across 29 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 223 days. Across the years with fuller monitoring, the share of Good days fell: an average of 65% in 1980–1982 versus 59% in 2023–2025.
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)
223
61%
Ozone
112
31%
Nitrogen dioxide (NO₂)
22
6%
Coarse particles (PM10)
8
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
228
121
14
2
0
0
43
74
175
PM2.5
2024
366
251
109
6
0
0
0
43
65
147
PM2.5
2023
365
166
180
15
2
2
0
52
82
250
PM2.5
2022
365
192
167
6
0
0
0
49
70
143
PM2.5
2021
365
162
196
7
0
0
0
52
72
129
PM2.5
2020
366
204
157
4
1
0
0
46
67
169
PM2.5
2019
365
205
157
3
0
0
0
47
68
105
PM2.5
2018
365
186
174
4
1
0
0
49
74
151
PM2.5
2017
365
223
138
4
0
0
0
44
67
129
PM2.5
2016
366
227
131
7
1
0
0
44
67
185
PM2.5
2015
365
199
163
3
0
0
0
48
67
112
PM2.5
2014
365
166
194
5
0
0
0
52
73
129
PM2.5
2013
365
146
218
1
0
0
0
53
74
101
PM2.5
2012
366
164
172
21
9
0
0
53
90
185
PM2.5
2011
365
167
189
8
1
0
0
52
75
195
PM2.5
2010
365
225
126
13
1
0
0
44
77
166
Ozone
2009
365
268
89
7
1
0
0
39
73
172
Ozone
2008
366
239
122
4
1
0
0
42
77
158
Ozone
2007
365
219
129
14
3
0
0
44
84
166
Ozone
2006
364
224
129
11
0
0
0
44
77
150
Ozone
2005
365
215
118
20
11
1
0
45
97
203
Ozone
2004
366
252
98
15
1
0
0
40
71
187
Ozone
2003
365
232
108
17
8
0
0
42
87
187
Ozone
2002
365
188
145
23
8
1
0
49
93
201
PM2.5
2001
365
108
223
22
11
1
0
59
100
208
PM2.5
2000
366
110
243
11
2
0
0
59
89
156
PM2.5
1999
365
101
219
35
10
0
0
61
105
197
PM2.5
1998
365
245
97
15
8
0
0
42
87
182
NO2
1997
365
278
75
8
2
2
0
41
74
222
NO2
1996
366
300
49
12
3
2
0
39
64
212
NO2
1995
365
279
56
17
8
5
0
40
87
212
NO2
1994
365
267
79
11
6
2
0
41
80
235
NO2
1993
365
293
57
12
3
0
0
39
64
190
NO2
1992
366
294
52
17
3
0
0
38
71
177
NO2
1991
365
250
68
25
13
9
0
42
115
239
NO2
1990
365
266
71
20
7
1
0
41
93
206
NO2
1989
365
237
87
25
12
4
0
44
105
222
NO2
1988
366
245
61
22
24
14
0
42
156
233
NO2
1987
365
251
70
24
10
10
0
43
119
300
NO2
1986
365
248
88
21
7
1
0
43
90
206
NO2
1985
365
263
71
23
8
0
0
42
93
200
NO2
1984
366
252
83
20
7
4
0
43
97
224
NO2
1983
363
238
81
21
14
9
0
42
119
260
NO2
1982
365
239
97
19
10
0
0
43
87
200
NO2
1981
358
232
90
20
6
10
0
44
101
232
NO2
1980
366
242
88
18
16
2
0
41
98
229
CO
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
