Daily Air Quality Index summaries from EPA monitors in Lenawee, Michigan, 1993–2025.
69%
Good days in 2025
41
Median daily AQI, 2025
7
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 Lenawee, Michigan on 365 days. 253 of those days (69%) were in the Good range, and the median daily AQI was 41. That median is about the same as the typical monitored county in Michigan (median 39 across 26 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 220 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 64% in 1994–1996 versus 63% in 2023–2025.
Years with fewer than 120 monitored days (1993) 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)
220
60%
Ozone
145
40%
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
253
105
7
0
0
0
41
66
147
PM2.5
2024
366
253
113
0
0
0
0
43
59
97
PM2.5
2023
364
188
166
8
2
0
0
50
70
165
PM2.5
2022
365
250
115
0
0
0
0
43
65
97
PM2.5
2021
322
188
134
0
0
0
0
46
64
93
PM2.5
2020
366
248
116
2
0
0
0
42
61
122
PM2.5
2019
358
233
125
0
0
0
0
44
61
91
PM2.5
2018
344
246
94
4
0
0
0
43
68
115
Ozone
2017
364
248
115
1
0
0
0
44
61
101
PM2.5
2016
361
223
136
2
0
0
0
44
62
119
PM2.5
2015
348
201
147
0
0
0
0
47
64
92
PM2.5
2014
345
174
168
3
0
0
0
50
67
129
PM2.5
2013
245
173
71
1
0
0
0
43
61
105
Ozone
2012
243
124
94
21
4
0
0
50
101
187
Ozone
2011
241
145
85
10
1
0
0
46
79
154
Ozone
2010
216
133
82
1
0
0
0
46
71
103
Ozone
2009
234
149
84
1
0
0
0
46
67
122
Ozone
2008
197
119
72
6
0
0
0
48
77
133
Ozone
2007
177
116
46
13
2
0
0
45
97
159
Ozone
2006
172
121
47
4
0
0
0
44
77
140
Ozone
2005
182
104
54
22
2
0
0
47
105
179
Ozone
2004
183
138
40
5
0
0
0
43
77
150
Ozone
2003
180
118
46
11
4
1
0
46
100
206
Ozone
2002
179
109
42
18
10
0
0
46
129
161
Ozone
2001
183
115
44
20
4
0
0
46
105
177
Ozone
2000
182
138
38
4
2
0
0
44
77
154
Ozone
1999
183
116
49
17
1
0
0
44
97
151
Ozone
1998
176
95
55
22
4
0
0
49
108
177
Ozone
1997
180
137
33
9
1
0
0
40
84
154
Ozone
1996
183
120
43
17
3
0
0
45
105
172
Ozone
1995
173
116
45
8
4
0
0
44
90
179
Ozone
1994
177
103
49
22
3
0
0
47
108
177
Ozone
1993
86
59
19
8
0
0
0
41
100
129
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 Michigan with a similar median AQI in 2025
