Daily Air Quality Index summaries from EPA monitors in Grafton, New Hampshire, 1990–2025.
84%
Good days in 2025
36
Median daily AQI, 2025
3
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Grafton, New Hampshire on 365 days. 305 of those days (84%) were in the Good range, and the median daily AQI was 36. That median is about the same as the typical monitored county in New Hampshire (median 37 across 7 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 238 days. Across the years with fuller monitoring, the share of Good days fell: an average of 92% in 1990–1992 versus 87% 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
238
65%
Fine particles (PM2.5)
127
35%
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
365
305
57
3
0
0
0
36
54
113
Ozone
2024
366
334
32
0
0
0
0
35
49
80
Ozone
2023
365
311
54
0
0
0
0
37
53
100
Ozone
2022
365
330
35
0
0
0
0
36
50
84
Ozone
2021
365
313
51
1
0
0
0
36
53
106
Ozone
2020
366
344
22
0
0
0
0
35
45
70
Ozone
2019
365
332
33
0
0
0
0
35
50
65
Ozone
2018
365
294
71
0
0
0
0
39
55
90
Ozone
2017
365
294
71
0
0
0
0
38
55
80
Ozone
2016
366
321
45
0
0
0
0
36
52
77
Ozone
2015
365
282
83
0
0
0
0
39
58
90
PM2.5
2014
365
282
82
1
0
0
0
40
56
101
Ozone
2013
365
288
77
0
0
0
0
38
57
84
Ozone
2012
366
285
81
0
0
0
0
38
57
97
Ozone
2011
365
254
111
0
0
0
0
40
60
93
Ozone
2010
365
281
84
0
0
0
0
38
58
94
Ozone
2009
363
276
87
0
0
0
0
38
58
95
Ozone
2008
364
333
30
1
0
0
0
33
49
122
Ozone
2007
364
326
30
7
1
0
0
33
51
156
Ozone
2006
362
314
46
2
0
0
0
34
54
122
Ozone
2005
362
314
45
3
0
0
0
35
53
133
Ozone
2004
364
332
28
4
0
0
0
34
49
147
Ozone
2003
345
303
37
5
0
0
0
35
52
140
Ozone
2002
364
324
35
4
1
0
0
34
52
177
Ozone
2001
361
315
37
9
0
0
0
35
58
140
Ozone
2000
365
349
15
1
0
0
0
33
46
122
Ozone
1999
360
320
35
5
0
0
0
35
54
126
Ozone
1998
363
314
42
7
0
0
0
35
58
136
Ozone
1997
363
338
24
1
0
0
0
34
48
150
Ozone
1996
366
349
16
0
1
0
0
33
46
151
Ozone
1995
364
344
19
1
0
0
0
33
46
101
Ozone
1994
359
344
14
1
0
0
0
33
47
122
Ozone
1993
361
343
16
2
0
0
0
31
44
105
Ozone
1992
357
338
11
6
2
0
0
32
46
166
Ozone
1991
360
326
28
5
1
0
0
33
48
166
Ozone
1990
357
325
26
6
0
0
0
34
49
129
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 New Hampshire with a similar median AQI in 2025
