Daily Air Quality Index summaries from EPA monitors in Madison, Ohio, 1991–2025.
79%
Good days in 2025
43
Median daily AQI, 2025
5
Days above 100 in 2025
244
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Madison, Ohio on 244 days. 193 of those days (79%) were in the Good range, and the median daily AQI was 43. That median is about the same as the typical monitored county in Ohio (median 43 across 36 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 244 days. Across the years with fuller monitoring, the share of Good days rose: an average of 57% in 1991–1993 versus 81% in 2023–2025.
EPA did not report an AQI for every day of 2025 here (244 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
244
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
244
193
46
5
0
0
0
43
71
112
Ozone
2024
245
203
42
0
0
0
0
44
61
100
Ozone
2023
243
197
44
2
0
0
0
44
64
105
Ozone
2022
244
218
26
0
0
0
0
39
51
90
Ozone
2021
229
212
17
0
0
0
0
39
50
84
Ozone
2020
245
220
25
0
0
0
0
39
51
84
Ozone
2019
245
209
36
0
0
0
0
42
54
93
Ozone
2018
244
209
34
1
0
0
0
41
58
101
Ozone
2017
244
211
32
1
0
0
0
41
54
105
Ozone
2016
213
161
50
2
0
0
0
43
64
112
Ozone
2015
214
172
41
1
0
0
0
42
64
108
Ozone
2014
205
169
33
3
0
0
0
43
58
108
Ozone
2013
213
177
36
0
0
0
0
42
61
97
Ozone
2012
214
126
78
9
1
0
0
47
90
174
Ozone
2011
213
146
53
14
0
0
0
44
84
143
Ozone
2010
210
132
70
8
0
0
0
47
84
126
Ozone
2009
214
169
44
1
0
0
0
41
67
112
Ozone
2008
213
142
67
4
0
0
0
45
77
122
Ozone
2007
212
108
77
25
2
0
0
50
105
164
Ozone
2006
214
123
76
15
0
0
0
47
97
147
Ozone
2005
214
120
62
29
3
0
0
48
108
174
Ozone
2004
214
150
52
12
0
0
0
44
87
129
Ozone
2003
212
128
65
15
3
1
0
47
97
202
Ozone
2002
214
106
57
35
16
0
0
51
143
192
Ozone
2001
214
124
64
23
3
0
0
48
108
192
Ozone
2000
213
124
69
16
2
2
0
48
100
203
Ozone
1999
210
101
59
39
11
0
0
51
136
187
Ozone
1998
207
90
65
39
13
0
0
61
140
197
Ozone
1997
214
120
64
22
8
0
0
46
119
172
Ozone
1996
212
114
54
30
13
1
0
50
136
213
Ozone
1995
211
104
58
40
7
2
0
51
133
205
Ozone
1994
211
118
60
27
6
0
0
48
119
195
Ozone
1993
175
88
59
26
2
0
0
50
119
182
Ozone
1992
210
144
50
14
2
0
0
44
97
156
Ozone
1991
201
103
68
25
5
0
0
50
119
166
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 Ohio with a similar median AQI in 2025
