Daily Air Quality Index summaries from EPA monitors in Ottawa, Michigan, 1988–2025.
71%
Good days in 2025
40
Median daily AQI, 2025
8
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 Ottawa, Michigan on 365 days. 260 of those days (71%) were in the Good range, and the median daily AQI was 40. 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 209 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 65% in 1989–1991 versus 64% in 2023–2025.
Years with fewer than 120 monitored days (1988, 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)
209
57%
Ozone
153
42%
Coarse particles (PM10)
3
1%
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
260
97
7
1
0
0
40
68
159
PM2.5
2024
365
257
107
1
0
0
0
41
63
105
Ozone
2023
356
176
172
5
2
1
0
51
74
227
PM2.5
2022
332
194
134
2
2
0
0
46
67
164
PM2.5
2021
365
186
175
4
0
0
0
49
71
108
PM2.5
2020
365
303
56
6
0
0
0
35
59
150
Ozone
2019
360
300
60
0
0
0
0
37
61
100
Ozone
2018
289
224
61
4
0
0
0
40
64
115
Ozone
2017
245
205
40
0
0
0
0
40
61
97
Ozone
2016
166
131
28
7
0
0
0
41
74
133
Ozone
2015
161
133
27
1
0
0
0
42
64
122
Ozone
2014
177
139
34
4
0
0
0
43
74
112
Ozone
2013
243
164
77
2
0
0
0
43
69
115
Ozone
2012
243
141
81
19
2
0
0
46
93
161
Ozone
2011
242
161
74
4
3
0
0
43
71
156
Ozone
2010
241
152
85
4
0
0
0
44
74
119
Ozone
2009
295
201
92
2
0
0
0
42
68
140
Ozone
2008
359
174
183
2
0
0
0
51
75
147
PM2.5
2007
362
154
191
12
5
0
0
54
86
169
PM2.5
2006
227
141
74
9
3
0
0
44
85
200
Ozone
2005
241
117
96
24
4
0
0
51
101
182
Ozone
2004
239
153
84
2
0
0
0
42
84
126
Ozone
2003
242
135
89
14
4
0
0
47
90
192
Ozone
2002
237
125
84
19
9
0
0
49
108
182
Ozone
2001
241
124
92
20
5
0
0
49
101
172
Ozone
2000
244
151
86
5
2
0
0
44
84
190
Ozone
1999
241
125
84
26
6
0
0
49
108
179
Ozone
1998
205
134
42
26
3
0
0
44
122
185
Ozone
1997
190
141
33
12
4
0
0
41
97
166
Ozone
1996
183
150
27
4
0
2
0
41
71
202
Ozone
1995
179
133
29
15
2
0
0
39
97
172
Ozone
1994
182
118
44
15
5
0
0
44
108
190
Ozone
1992
116
83
21
9
3
0
0
42
105
179
Ozone
1991
214
125
43
23
16
7
0
44
159
238
Ozone
1990
224
155
45
16
6
2
0
41
105
202
Ozone
1989
236
160
40
28
6
2
0
43
112
221
Ozone
1988
9
9
0
0
0
0
0
12
19
19
PM10
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
