New London County, Connecticut air quality history
Daily Air Quality Index summaries from EPA monitors in New London, Connecticut, 1981–2025.
81%
Good days in 2025
38
Median daily AQI, 2025
8
Days above 100 in 2025
364
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for New London, Connecticut on 364 days. 296 of those days (81%) were in the Good range, and the median daily AQI was 38. That median is lower than the typical monitored county in Connecticut (median 41 across 8 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 192 days. Across the years with fuller monitoring, the share of Good days rose: an average of 34% in 1981–1983 versus 79% 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
Fine particles (PM2.5)
192
53%
Ozone
172
47%
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
364
296
60
8
0
0
0
38
60
136
PM2.5
2024
365
309
51
5
0
0
0
37
55
126
PM2.5
2023
363
258
95
7
3
0
0
41
61
166
PM2.5
2022
365
290
71
4
0
0
0
39
57
108
PM2.5
2021
363
277
79
7
0
0
0
39
60
129
PM2.5
2020
365
274
87
3
1
0
0
41
61
172
PM2.5
2019
364
295
62
7
0
0
0
40
56
129
PM2.5
2018
315
260
49
6
0
0
0
39
56
140
Ozone
2017
348
286
54
6
2
0
0
39
56
161
Ozone
2016
357
282
65
9
1
0
0
38
61
154
PM2.5
2015
359
265
82
11
1
0
0
40
61
151
PM2.5
2014
355
236
118
1
0
0
0
43
65
104
PM2.5
2013
349
125
217
4
3
0
0
53
66
164
PM2.5
2012
339
166
159
10
4
0
0
51
71
197
PM2.5
2011
238
167
60
10
1
0
0
42
74
156
Ozone
2010
364
245
111
8
0
0
0
41
68
126
PM2.5
2009
356
225
125
6
0
0
0
43
71
143
PM2.5
2008
349
196
142
9
2
0
0
47
74
172
PM2.5
2007
331
185
123
17
6
0
0
46
81
179
PM2.5
2006
237
152
75
6
3
1
0
45
83
205
Ozone
2005
237
142
79
13
3
0
0
46
87
169
Ozone
2004
239
168
67
3
1
0
0
42
71
174
Ozone
2003
237
138
80
14
3
2
0
46
80
208
Ozone
2002
234
143
71
13
5
2
0
44
93
223
Ozone
2001
235
127
89
13
6
0
0
49
90
185
Ozone
2000
252
153
84
13
1
1
0
44
87
220
Ozone
1999
239
149
65
16
8
1
0
46
101
228
Ozone
1998
240
182
42
13
2
1
0
42
90
204
Ozone
1997
214
139
50
9
13
3
0
44
112
251
Ozone
1996
212
137
59
10
5
1
0
44
93
216
Ozone
1995
235
191
31
5
5
3
0
38
77
215
Ozone
1994
219
147
50
17
5
0
0
41
105
200
Ozone
1993
233
175
36
15
7
0
0
42
97
197
Ozone
1992
240
183
36
15
6
0
0
38
93
190
Ozone
1991
235
163
37
16
14
5
0
41
133
219
Ozone
1990
238
172
34
20
9
3
0
38
115
223
Ozone
1989
225
129
60
22
8
6
0
45
122
226
Ozone
1988
223
143
42
19
10
9
0
46
140
226
Ozone
1987
202
118
48
18
6
12
0
48
140
235
Ozone
1986
207
131
41
25
6
4
0
45
126
221
Ozone
1985
209
120
42
25
13
9
0
48
151
245
Ozone
1984
178
95
37
16
14
16
0
50
197
275
Ozone
1983
173
54
37
20
25
37
0
97
237
291
Ozone
1982
143
46
34
31
15
17
0
80
203
244
Ozone
1981
137
53
39
14
20
11
0
67
182
260
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 Connecticut with a similar median AQI in 2025
