Daily Air Quality Index summaries from EPA monitors in Simpson, Kentucky, 1991–2025.
93%
Good days in 2025
39
Median daily AQI, 2025
0
Days above 100 in 2025
243
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Simpson, Kentucky on 243 days. 227 of those days (93%) were in the Good range, and the median daily AQI was 39. That median is about the same as the typical monitored county in Kentucky (median 39 across 25 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 243 days. Across the years with fuller monitoring, the share of Good days rose: an average of 78% in 1991–1993 versus 87% in 2023–2025.
EPA did not report an AQI for every day of 2025 here (243 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
243
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
243
227
16
0
0
0
0
39
49
74
Ozone
2024
242
204
38
0
0
0
0
43
58
97
Ozone
2023
244
204
33
7
0
0
0
43
61
122
Ozone
2022
241
217
24
0
0
0
0
39
50
93
Ozone
2021
243
222
21
0
0
0
0
37
50
90
Ozone
2020
221
217
4
0
0
0
0
36
46
67
Ozone
2019
244
222
22
0
0
0
0
40
50
67
Ozone
2018
243
212
31
0
0
0
0
38
51
93
Ozone
2017
237
220
17
0
0
0
0
40
49
87
Ozone
2016
243
217
25
1
0
0
0
40
51
101
Ozone
2015
208
179
28
1
0
0
0
39
51
101
Ozone
2014
245
217
28
0
0
0
0
39
54
87
Ozone
2013
235
222
13
0
0
0
0
38
48
67
Ozone
2012
239
192
42
5
0
0
0
43
74
129
Ozone
2011
241
164
72
5
0
0
0
45
77
143
Ozone
2010
243
160
76
7
0
0
0
46
84
112
Ozone
2009
244
199
43
2
0
0
0
40
61
119
Ozone
2008
245
160
81
4
0
0
0
45
80
115
Ozone
2007
245
124
87
32
2
0
0
50
108
161
Ozone
2006
243
176
57
10
0
0
0
44
80
147
Ozone
2005
245
150
76
18
1
0
0
47
93
159
Ozone
2004
245
183
59
3
0
0
0
42
71
133
Ozone
2003
245
160
77
8
0
0
0
44
87
147
Ozone
2002
245
175
49
20
1
0
0
43
97
154
Ozone
2001
242
156
67
16
3
0
0
46
97
166
Ozone
2000
244
161
59
21
3
0
0
45
100
172
Ozone
1999
352
218
68
53
13
0
0
40
126
195
Ozone
1998
358
244
69
35
9
1
0
40
105
201
Ozone
1997
349
261
70
14
3
1
0
36
80
206
Ozone
1996
355
263
77
14
1
0
0
39
80
166
Ozone
1995
357
238
86
31
2
0
0
41
97
179
Ozone
1994
346
268
66
12
0
0
0
38
80
143
Ozone
1993
362
299
56
6
1
0
0
36
61
154
NO2
1992
345
288
47
10
0
0
0
36
61
143
NO2
1991
122
82
34
6
0
0
0
43
93
150
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 Kentucky with a similar median AQI in 2025
