Daily Air Quality Index summaries from EPA monitors in Windham, Connecticut, 1988–2025.
94%
Good days in 2025
35
Median daily AQI, 2025
1
Days above 100 in 2025
362
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Windham, Connecticut on 362 days. 339 of those days (94%) were in the Good range, and the median daily AQI was 35. That median is lower than the typical monitored county in Connecticut (median 41 across 8 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 362 days. Across the years with fuller monitoring, the share of Good days rose: an average of 81% in 1994–1996 versus 94% in 2023–2025.
Years with fewer than 120 monitored days (1988, 1989, 1990, 1991, 1992, 1993) are shown in the table but left out of comparisons and trend statements.
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
362
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
362
339
22
1
0
0
0
35
47
108
Ozone
2024
359
340
17
2
0
0
0
34
46
122
Ozone
2023
359
340
17
2
0
0
0
34
46
112
Ozone
2022
355
338
17
0
0
0
0
35
46
93
Ozone
2021
361
331
29
1
0
0
0
34
48
140
Ozone
2020
356
345
11
0
0
0
0
35
44
87
Ozone
2019
360
344
15
1
0
0
0
36
46
105
Ozone
2018
358
332
20
6
0
0
0
34
47
129
Ozone
2017
355
334
17
4
0
0
0
34
46
140
Ozone
2016
358
331
23
3
1
0
0
35
48
154
Ozone
2015
356
326
27
3
0
0
0
35
48
129
Ozone
2014
354
328
25
1
0
0
0
34
48
101
Ozone
2013
359
328
28
3
0
0
0
36
50
119
Ozone
2012
358
317
32
9
0
0
0
34
54
147
Ozone
2011
212
193
16
3
0
0
0
34
50
140
Ozone
2010
326
282
39
5
0
0
0
36
61
122
Ozone
2009
359
338
19
2
0
0
0
31
45
150
Ozone
2008
364
335
25
4
0
0
0
33
49
115
Ozone
2007
361
314
31
14
2
0
0
33
64
172
Ozone
2006
363
318
32
11
2
0
0
32
58
172
Ozone
2005
353
299
37
13
4
0
0
33
67
195
Ozone
2004
347
314
25
7
1
0
0
32
50
182
Ozone
2003
363
317
32
12
2
0
0
35
61
185
Ozone
2002
363
295
34
23
8
3
0
35
93
214
Ozone
2001
363
296
38
15
10
4
0
37
87
210
Ozone
2000
316
255
46
11
3
1
0
35
71
209
Ozone
1999
350
278
45
19
7
1
0
38
80
203
Ozone
1998
362
280
58
17
6
1
0
38
93
208
Ozone
1997
342
282
36
13
9
2
0
36
77
220
Ozone
1996
231
190
29
9
3
0
0
32
80
182
Ozone
1995
284
227
31
16
8
2
0
38
100
215
Ozone
1994
354
284
41
18
10
1
0
37
84
201
Ozone
1993
60
60
0
0
0
0
0
15
34
44
PM10
1992
57
56
1
0
0
0
0
14
32
55
PM10
1991
54
54
0
0
0
0
0
19
35
50
PM10
1990
61
61
0
0
0
0
0
17
30
44
PM10
1989
61
61
0
0
0
0
0
19
32
46
PM10
1988
28
28
0
0
0
0
0
19
32
40
PM10
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 Connecticut with a similar median AQI in 2025
