Median AQI
38
Good
Connecticut · County air quality · 2025
New London County, Connecticut
Median AQI 38 (Good). 81.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 38
- Median AQI
- 81.3%
- Good-air days
- 0
- Unhealthy days
- 59%
- Cleaner than US counties
New London County's 2025 annual median AQI is 38 (Good), with 81.3% Good days
According to the U.S. EPA Air Quality System, New London County, Connecticut posted a 2025 median AQI of 38 (Good) across 364 monitored days, with 81.3% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- New London County's 81.3% Good-day share places it cleaner than 59% of US counties in 2025.
- Closest median-AQI peer
- Adams County (94.7% Good, median AQI 38) is the closest nationwide median-AQI peer to New London County.
- 2020–2025 trend
- New London County's floor-qualifying Good-day share is improving from 2020 to 2025 (75.1% → 81.3%).
- Median AQI
- Median AQI: 38
The verdict
According to EPA Air Quality System monitoring data, New London County's air is good on balance, cleaner than the median US county, a median AQI of 38 with 81.3% of 364 monitored days in the Good band, driven mainly by PM2.5.
- 38
- median AQI · Good
- 81.3%
- days rated Good
- PM2.5
- main pollutant
- 59%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 136.
Annual release change
What changed in the 2025 EPA annual release
- New London County's Good-day share fell from 84.7% to 81.3% between the 2024 and 2025 EPA annual releases, a change of -3.3 percentage points.
- New London County's peak single-day AQI rose from 126 to 136 between the 2024 and 2025 EPA annual releases, a change of +10 points.
Data updated August 2026
- Good · 296 d · 81.3%
- Moderate · 60 d · 16.5%
- USG · 8 d · 2.2%
How did New London County's air break down in 2025?
Across 364 monitored days, 296 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 136 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 364 days monitored. Median AQI: 38 (Good).
Insights: New London County, Connecticut. EPA monitors recorded a median Air Quality Index of 38 across 364 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 296 (81%) fell in the Good band (AQI 0–50), 60 (16%) registered Moderate readings, and 8 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 60, while the worst single-day peak hit 136 (USG). Residents averaged about 24.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (192 days), Ozone (172 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +6.3 points and the median AQI moved -3 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 136, usg but never Unhealthy. Nearby counties show comparable readings: Fairfield (64.7% good, AQI 44); Hartford (68.0% good, AQI 42); Litchfield (81.4% good, AQI 39); Middlesex (77.5% good, AQI 42); New Haven (67.1% good, AQI 43); Tolland (83.7% good, AQI 40).
Air Quality Summary
Good Days
81.3%
296 of 364 monitored days
6.3pp vs 75% target
Max AQI Recorded
136
USG
Health Grade
Good
90th-pct AQI 60
New London County, Good days share 81.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
New London County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 364 monitored days across EPA AQI categories.
Good
296
81%
Moderate
60
16%
USG
8
2%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in New London County.
- PM2.5 · 192 days · 52.7%
- Ozone · 172 days · 47.3%
Health Impact Assessment
Good
New London County's air quality is rated Good based on 81.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 81.3% of monitored days in 2025, with a median AQI of 38. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 192 of 364 monitored days.
5-Year Air Quality Trend
Air quality is improving in New London County. Highest Good-day share: 2024 (84.7%, 309 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 274 | 87 | 3 | 1 | 41 | 172 |
| 2021 | 277 | 79 | 7 | 0 | 39 | 129 |
| 2022 | 290 | 71 | 4 | 0 | 39 | 108 |
| 2023 | 258 | 95 | 7 | 3 | 41 | 166 |
| 2024 | 309 | 51 | 5 | 0 | 37 | 126 |
| 2025 | 296 | 60 | 8 | 0 | 38 | 136 |
How does New London County compare?
How New London County compares
Good-day share better than US avg
New London County 81.3%
Adams County, Illinois 94.7%
US average 76.0%
Median AQI better than US avg
New London County 38
Adams County, Illinois 38
US average 39
Unhealthy days / yr better than US avg
New London County 0
Adams County, Illinois 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as New London County (38), not geographic neighbors.
Adams County, Illinois
Median AQI 38 · 94.7% Good-day share
Albemarle County, Virginia
Median AQI 38 · 81.0% Good-day share
Alexander County, North Carolina
Median AQI 38 · 93.5% Good-day share
Amador County, California
Median AQI 38 · 87.4% Good-day share
Anoka County, Minnesota
Median AQI 38 · 74.1% Good-day share
Avery County, North Carolina
Median AQI 38 · 92.3% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Pulaski County, Kentucky
81.4% Good-day share · median AQI 40
Lawrence County, Tennessee
81.5% Good-day share · median AQI 33
Mitchell County, North Carolina
81.5% Good-day share · median AQI 31
Swain County, North Carolina
81.1% Good-day share · median AQI 37
Clay County, Alabama
81.1% Good-day share · median AQI 33
Guaynabo County, Puerto Rico
81.6% Good-day share · median AQI 33
Connecticut counties on the map
Geographic containment only, other monitored counties in Connecticut, independent of AQI or pollutant match.
What New London County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 38 means for exposure. Health guidance
- See how New London County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare New London County with its Connecticut neighbours before drawing a conclusion about the region. All of Connecticut
Based on 364 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in New London County, Connecticut? ▼
New London County has a median Air Quality Index (AQI) of 38, rated "Good." 81.3% of monitored days (296 out of 364) had good air quality in 2025.
What is the main pollutant in New London County? ▼
The primary pollutant in New London County is Fine Particles (PM2.5), which was the main AQI driver on 192 days (53% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does New London County have? ▼
In 2025, New London County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 136.
Is the air quality in New London County getting better or worse? ▼
Air quality in New London County is improving across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2024 at 84.7% (309 of 365 days). Lowest qualifying Good-day share: 2023 at 71.1% (258 of 363 days).
What does AQI 38 mean for health? ▼
New London County's median AQI of 38 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does New London County compare to other counties in Connecticut? ▼
New London County has 81.3% good air days. Nearby counties in Connecticut: Fairfield (64.7% good), Hartford (68.0% good), Litchfield (81.4% good), Middlesex (77.5% good), New Haven (67.1% good), Tolland (83.7% good).
What is the 90th percentile AQI in New London County? ▼
The 90th percentile AQI for New London County is 60, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 136 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for New London County, Connecticut · 2020–2025
Share this annual record
Send the source-year summary or download its ready-to-use data card.
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.