Daily Air Quality Index summaries from EPA monitors in Door, Wisconsin, 1989–2025.
86%
Good days in 2025
38
Median daily AQI, 2025
1
Days above 100 in 2025
198
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Door, Wisconsin on 198 days. 170 of those days (86%) were in the Good range, and the median daily AQI was 38. That median is about the same as the typical monitored county in Wisconsin (median 38 across 29 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 198 days. Across the years with fuller monitoring, the share of Good days rose: an average of 70% in 1989–1991 versus 83% in 2023–2025.
EPA did not report an AQI for every day of 2025 here (198 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.
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
Ozone
198
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
198
170
27
1
0
0
0
38
64
108
Ozone
2024
202
175
25
2
0
0
0
37
58
108
Ozone
2023
204
155
40
8
1
0
0
41
87
159
Ozone
2022
205
176
24
5
0
0
0
36
71
147
Ozone
2021
206
173
30
3
0
0
0
39
61
126
Ozone
2020
205
184
17
4
0
0
0
36
51
150
Ozone
2019
201
191
9
1
0
0
0
35
47
112
Ozone
2018
224
199
21
4
0
0
0
40
51
133
Ozone
2017
236
213
20
3
0
0
0
37
50
112
Ozone
2016
188
158
22
8
0
0
0
36
67
150
Ozone
2015
202
175
22
5
0
0
0
39
61
129
Ozone
2014
189
163
24
2
0
0
0
37
67
133
Ozone
2013
195
155
38
2
0
0
0
38
71
126
Ozone
2012
179
136
24
14
5
0
0
38
105
187
Ozone
2011
196
176
15
4
1
0
0
36
51
161
Ozone
2010
189
161
21
5
2
0
0
37
67
172
Ozone
2009
192
166
22
4
0
0
0
35
58
150
Ozone
2008
190
158
31
1
0
0
0
40
71
133
Ozone
2007
198
143
33
16
6
0
0
42
112
174
Ozone
2006
186
150
28
6
2
0
0
38
80
195
Ozone
2005
186
125
37
15
7
2
0
42
126
203
Ozone
2004
175
138
27
8
2
0
0
39
74
156
Ozone
2003
203
156
33
10
3
1
0
44
84
214
Ozone
2002
240
167
58
8
7
0
0
41
87
192
Ozone
2001
242
169
55
9
7
2
0
42
82
207
Ozone
2000
230
174
48
5
3
0
0
39
67
177
Ozone
1999
235
166
46
9
13
1
0
41
100
208
Ozone
1998
183
121
43
12
6
1
0
44
101
203
Ozone
1997
184
142
26
9
5
2
0
40
90
212
Ozone
1996
183
141
31
5
5
1
0
43
87
217
Ozone
1995
184
132
29
15
6
2
0
42
108
212
Ozone
1994
183
129
35
12
6
1
0
41
101
208
Ozone
1993
174
152
15
6
1
0
0
35
54
166
Ozone
1992
184
149
22
13
0
0
0
33
80
147
Ozone
1991
182
133
18
19
9
3
0
40
126
228
Ozone
1990
180
128
30
13
5
4
0
41
115
221
Ozone
1989
158
106
27
20
4
1
0
42
122
202
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
