Daily Air Quality Index summaries from EPA monitors in Huron, Michigan, 1980–2025.
90%
Good days in 2025
38
Median daily AQI, 2025
2
Days above 100 in 2025
212
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Huron, Michigan on 212 days. 190 of those days (90%) were in the Good range, and the median daily AQI was 38. 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 ozone on 212 days. Across the years with fuller monitoring, the share of Good days rose: an average of 77% in 1980–1995 versus 88% in 2023–2025.
EPA did not report an AQI for every day of 2025 here (212 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.
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
Ozone
212
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
212
190
20
2
0
0
0
38
51
108
Ozone
2024
245
216
28
1
0
0
0
38
51
119
Ozone
2023
240
209
27
4
0
0
0
39
58
133
Ozone
2022
243
227
15
1
0
0
0
35
49
122
Ozone
2021
246
221
23
2
0
0
0
37
51
101
Ozone
2020
266
246
13
7
0
0
0
36
48
150
Ozone
2019
259
250
9
0
0
0
0
36
46
90
Ozone
2018
241
212
26
3
0
0
0
38
54
122
Ozone
2017
241
224
17
0
0
0
0
37
49
97
Ozone
2016
183
163
15
5
0
0
0
38
51
119
Ozone
2015
182
162
18
2
0
0
0
39
51
129
Ozone
2014
167
152
14
1
0
0
0
38
50
115
Ozone
2013
181
153
27
1
0
0
0
40
58
133
Ozone
2012
183
127
38
15
3
0
0
44
100
177
Ozone
2011
183
161
19
3
0
0
0
40
51
126
Ozone
2010
183
155
26
2
0
0
0
40
64
126
Ozone
2009
175
160
12
3
0
0
0
38
50
119
Ozone
2008
183
153
28
2
0
0
0
39
54
122
Ozone
2007
182
135
28
16
3
0
0
41
101
177
Ozone
2006
175
144
27
3
1
0
0
40
67
164
Ozone
2005
177
138
29
9
1
0
0
41
87
151
Ozone
2004
183
164
16
2
1
0
0
37
51
156
Ozone
2003
177
134
32
6
5
0
0
41
87
166
Ozone
2002
183
131
35
12
5
0
0
42
93
192
Ozone
2001
169
116
36
12
4
1
0
44
101
213
Ozone
2000
182
144
33
5
0
0
0
38
67
143
Ozone
1999
179
127
34
11
6
1
0
41
105
201
Ozone
1998
183
129
38
12
4
0
0
41
97
182
Ozone
1997
183
153
23
5
2
0
0
35
61
169
Ozone
1996
183
147
23
11
2
0
0
40
87
151
Ozone
1995
177
131
34
11
0
1
0
39
93
203
Ozone
1994
181
136
31
11
3
0
0
40
93
187
Ozone
1993
99
81
13
4
1
0
0
35
80
154
Ozone
1980
359
294
41
14
8
2
0
35
84
224
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
