Daily Air Quality Index summaries from EPA monitors in Jefferson, Tennessee, 1992–2025.
91%
Good days in 2025
41
Median daily AQI, 2025
0
Days above 100 in 2025
237
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Jefferson, Tennessee on 237 days. 215 of those days (91%) were in the Good range, and the median daily AQI was 41. That median is about the same as the typical monitored county in Tennessee (median 39 across 23 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 237 days. Across the years with fuller monitoring, the share of Good days rose: an average of 48% in 1992–1994 versus 90% in 2023–2025.
EPA did not report an AQI for every day of 2025 here (237 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
237
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
237
215
22
0
0
0
0
41
50
93
Ozone
2024
244
222
21
1
0
0
0
40
50
105
Ozone
2023
241
210
29
2
0
0
0
42
54
112
Ozone
2022
244
219
25
0
0
0
0
41
51
87
Ozone
2021
235
199
36
0
0
0
0
41
58
100
Ozone
2020
240
232
8
0
0
0
0
37
48
74
Ozone
2019
234
197
37
0
0
0
0
44
58
93
Ozone
2018
244
202
42
0
0
0
0
42
61
100
Ozone
2017
191
148
42
1
0
0
0
43
61
101
Ozone
2016
239
158
79
2
0
0
0
47
74
133
Ozone
2015
245
183
61
1
0
0
0
44
71
101
Ozone
2014
245
190
55
0
0
0
0
44
64
93
Ozone
2013
242
197
43
2
0
0
0
43
61
101
Ozone
2012
245
152
84
6
2
1
0
46
80
206
Ozone
2011
245
162
75
8
0
0
0
46
80
147
Ozone
2010
241
153
73
15
0
0
0
46
90
140
Ozone
2009
239
190
47
2
0
0
0
40
67
140
Ozone
2008
243
144
85
13
1
0
0
48
93
164
Ozone
2007
245
103
110
29
3
0
0
61
105
159
Ozone
2006
234
134
81
17
2
0
0
48
97
179
Ozone
2005
240
120
87
30
3
0
0
51
112
200
Ozone
2004
243
153
77
13
0
0
0
46
84
140
Ozone
2003
245
169
62
11
3
0
0
44
87
187
Ozone
2002
243
140
49
37
16
1
0
48
147
204
Ozone
2001
232
130
73
21
8
0
0
48
101
182
Ozone
2000
242
142
64
25
11
0
0
47
112
187
Ozone
1999
217
90
61
50
14
2
0
67
140
210
Ozone
1998
207
71
59
50
22
5
0
80
159
205
Ozone
1997
214
84
75
40
14
1
0
61
140
202
Ozone
1996
213
72
78
48
14
1
0
74
140
207
Ozone
1995
213
56
79
53
23
2
0
84
151
212
Ozone
1994
209
105
66
33
5
0
0
50
112
169
Ozone
1993
211
63
71
53
24
0
0
77
154
197
Ozone
1992
207
134
53
14
6
0
0
45
100
179
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 Tennessee with a similar median AQI in 2025
