Daily Air Quality Index summaries from EPA monitors in Ozaukee, Wisconsin, 1980–2025.
76%
Good days in 2025
36
Median daily AQI, 2025
15
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 Ozaukee, Wisconsin on 365 days. 277 of those days (76%) were in the Good range, and the median daily AQI was 36. 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 213 days. Across the years with fuller monitoring, the share of Good days fell: an average of 86% in 1980–1982 versus 72% 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)
213
58%
Ozone
152
42%
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
277
73
13
2
0
0
36
67
167
PM2.5
2024
366
296
61
7
2
0
0
37
61
161
Ozone
2023
363
219
126
14
2
2
0
45
84
210
PM2.5
2022
307
228
74
4
1
0
0
41
64
159
Ozone
2021
364
241
116
7
0
0
0
43
67
129
PM2.5
2020
365
269
91
4
1
0
0
40
62
164
PM2.5
2019
363
271
89
3
0
0
0
40
61
108
PM2.5
2018
363
254
102
5
2
0
0
43
68
169
Ozone
2017
348
276
64
8
0
0
0
40
64
136
Ozone
2016
355
269
77
8
1
0
0
38
63
172
Ozone
2015
365
260
100
5
0
0
0
40
64
122
PM2.5
2014
358
258
94
6
0
0
0
41
66
119
PM2.5
2013
352
230
118
4
0
0
0
42
67
112
PM2.5
2012
364
201
139
18
6
0
0
47
88
192
PM2.5
2011
235
174
53
7
1
0
0
40
71
182
Ozone
2010
253
183
64
5
1
0
0
42
71
161
Ozone
2009
252
186
63
2
1
0
0
41
71
164
Ozone
2008
248
160
87
1
0
0
0
43
72
124
Ozone
2007
248
138
93
14
3
0
0
47
87
164
Ozone
2006
247
158
83
4
2
0
0
44
74
169
Ozone
2005
243
140
78
16
7
2
0
45
101
205
Ozone
2004
244
175
57
12
0
0
0
39
71
140
Ozone
2003
219
142
56
16
4
1
0
46
100
207
Ozone
2002
244
150
69
16
8
1
0
45
101
201
Ozone
2001
243
138
84
10
9
2
0
47
93
214
Ozone
2000
240
152
80
4
4
0
0
44
76
164
Ozone
1999
215
117
70
14
14
0
0
47
126
192
Ozone
1998
184
102
55
17
10
0
0
48
122
200
Ozone
1997
184
138
34
8
2
2
0
43
84
220
Ozone
1996
184
147
21
11
4
1
0
42
84
207
Ozone
1995
184
116
42
16
4
6
0
46
133
212
Ozone
1994
212
156
35
12
8
1
0
41
96
245
Ozone
1993
212
183
20
7
2
0
0
37
67
164
Ozone
1992
214
179
21
13
1
0
0
34
87
151
Ozone
1991
209
144
40
15
8
2
0
41
105
228
Ozone
1990
213
162
32
15
3
1
0
41
97
203
Ozone
1989
214
143
44
19
5
3
0
44
108
227
Ozone
1988
213
125
37
19
22
10
0
45
161
229
Ozone
1987
214
147
34
18
10
5
0
42
129
294
Ozone
1986
296
249
32
12
2
1
0
33
77
201
Ozone
1985
348
288
39
13
8
0
0
33
87
187
Ozone
1984
352
314
19
15
4
0
0
32
61
192
Ozone
1983
317
263
20
19
7
8
0
31
105
248
Ozone
1982
351
299
30
14
8
0
0
33
80
190
Ozone
1981
320
280
21
10
7
2
0
27
69
208
Ozone
1980
183
154
11
12
5
1
0
20
97
246
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
