Daily Air Quality Index summaries from EPA monitors in Adams, Pennsylvania, 1990–2025.
74%
Good days in 2025
42
Median daily AQI, 2025
0
Days above 100 in 2025
351
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Adams, Pennsylvania on 351 days. 261 of those days (74%) were in the Good range, and the median daily AQI was 42. That median is about the same as the typical monitored county in Pennsylvania (median 40 across 38 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 251 days. Across the years with fuller monitoring, the share of Good days fell: an average of 72% in 1990–1992 versus 63% in 2023–2025.
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
251
72%
Fine particles (PM2.5)
99
28%
Carbon monoxide (CO)
1
<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
351
261
90
0
0
0
0
42
61
100
Ozone
2024
366
231
132
3
0
0
0
44
67
131
Ozone
2023
365
188
166
7
3
1
0
50
77
241
PM2.5
2022
365
221
144
0
0
0
0
47
60
97
PM2.5
2021
364
206
155
3
0
0
0
47
67
129
PM2.5
2020
366
280
86
0
0
0
0
42
58
88
Ozone
2019
365
243
122
0
0
0
0
45
63
87
Ozone
2018
365
243
120
2
0
0
0
44
64
105
Ozone
2017
365
238
126
1
0
0
0
45
60
129
Ozone
2016
366
239
122
5
0
0
0
44
69
119
Ozone
2015
365
176
188
1
0
0
0
51
68
101
PM2.5
2014
365
222
141
2
0
0
0
45
65
102
Ozone
2013
365
173
189
3
0
0
0
52
71
120
PM2.5
2012
365
160
194
11
0
0
0
53
80
146
PM2.5
2011
362
121
236
5
0
0
0
55
75
140
PM2.5
2010
365
142
211
10
2
0
0
54
84
166
PM2.5
2009
365
155
208
2
0
0
0
53
74
126
PM2.5
2008
365
160
186
18
1
0
0
53
80
159
PM2.5
2007
364
143
194
27
0
0
0
54
97
143
PM2.5
2006
365
164
188
13
0
0
0
52
87
132
PM2.5
2005
364
120
217
26
1
0
0
58
93
161
PM2.5
2004
366
124
219
23
0
0
0
57
90
129
PM2.5
2003
365
120
226
17
2
0
0
57
90
195
PM2.5
2002
365
132
176
35
17
5
0
56
129
206
PM2.5
2001
365
117
192
42
14
0
0
59
119
166
PM2.5
2000
366
144
191
28
3
0
0
55
93
179
PM2.5
1999
364
160
173
24
7
0
0
54
97
166
Ozone
1998
362
233
75
35
18
1
0
41
122
203
Ozone
1997
358
256
60
36
6
0
0
40
105
192
Ozone
1996
356
260
66
25
5
0
0
38
93
166
Ozone
1995
355
249
59
32
15
0
0
39
112
200
Ozone
1994
358
248
69
34
6
1
0
40
105
203
Ozone
1993
348
246
58
29
14
1
0
38
119
204
Ozone
1992
356
275
60
20
1
0
0
34
93
187
Ozone
1991
356
227
67
41
19
2
0
41
136
208
Ozone
1990
363
268
48
37
9
1
0
38
112
203
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 Pennsylvania with a similar median AQI in 2025
