Daily Air Quality Index summaries from EPA monitors in Allegan, Michigan, 1990–2025.
64%
Good days in 2025
44
Median daily AQI, 2025
14
Days above 100 in 2025
363
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Allegan, Michigan on 363 days. 232 of those days (64%) were in the Good range, and the median daily AQI was 44. That median is higher than the typical monitored county in Michigan (median 39 across 26 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 202 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 67% in 1993–1995 versus 65% in 2023–2025.
Years with fewer than 120 monitored days (1990, 1991, 1992) 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)
202
56%
Ozone
161
44%
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
363
232
117
12
2
0
0
44
75
151
PM2.5
2024
351
222
125
4
0
0
0
46
66
115
PM2.5
2023
360
246
102
11
1
0
0
42
80
161
Ozone
2022
344
256
82
4
2
0
0
40
64
195
Ozone
2021
361
245
107
9
0
0
0
42
64
136
PM2.5
2020
359
275
78
6
0
0
0
37
58
136
Ozone
2019
276
224
48
4
0
0
0
39
62
115
Ozone
2018
286
218
60
8
0
0
0
40
67
150
Ozone
2017
281
207
70
4
0
0
0
41
67
115
Ozone
2016
240
174
57
9
0
0
0
43
71
150
Ozone
2015
243
169
70
4
0
0
0
42
71
147
Ozone
2014
240
164
69
6
1
0
0
44
80
151
Ozone
2013
240
150
82
7
1
0
0
44
80
154
Ozone
2012
240
139
65
25
11
0
0
47
122
195
Ozone
2011
242
163
70
6
3
0
0
40
77
179
Ozone
2010
244
156
83
5
0
0
0
44
80
122
Ozone
2009
243
163
75
4
1
0
0
44
77
166
Ozone
2008
241
152
81
7
1
0
0
46
80
187
Ozone
2007
241
134
80
21
4
2
0
48
112
204
Ozone
2006
286
170
99
13
4
0
0
46
84
185
Ozone
2005
362
154
166
32
8
2
0
54
108
208
PM2.5
2004
360
176
169
14
0
1
0
51
84
202
PM2.5
2003
355
154
174
20
6
1
0
53
95
201
PM2.5
2002
363
162
161
22
15
3
0
53
105
214
PM2.5
2001
364
141
187
27
9
0
0
55
100
192
PM2.5
2000
357
164
176
14
1
2
0
53
86
204
PM2.5
1999
342
159
147
26
9
1
0
52
102
214
PM2.5
1998
182
98
43
24
16
1
0
48
147
209
Ozone
1997
183
129
36
12
6
0
0
40
100
197
Ozone
1996
268
211
32
17
6
2
0
38
100
221
Ozone
1995
274
185
49
26
10
4
0
40
126
260
Ozone
1994
197
123
37
27
10
0
0
44
122
185
Ozone
1993
211
147
47
15
2
0
0
40
93
200
Ozone
1992
67
61
6
0
0
0
0
29
49
90
Ozone
1991
112
41
26
24
18
3
0
80
166
229
Ozone
1990
34
17
8
6
2
1
0
51
143
215
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
