New Haven Air Quality in Fall
Across 2019–2025, New Haven's fall (September–November) air quality had a median AQI of 39 (Good) over 637 monitored days in the New Haven-Milford, CT area. 0.3% of fall days (2 of 637) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 59.7% of days. The cleanest fall on record here was 2025 (median AQI 36, 0 days above 100) and the worst was 2023 (median 42, 1 day above 100, peak AQI 101).
- Good: 72.7%
- Moderate: 27.0%
- Unhealthy for Sensitive Groups: 0.3%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in New Haven
Today's main pollutant in New Haven is ground-level ozone (AQI 32). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
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How is the air in New Haven in fall?
Good on a typical day: median AQI 39 across 2019–2025, with 0.3% of fall days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓72.7% of fall days were Good (AQI 0–50), 27.0% Moderate (51–100).
- ✓2 days of 637 reached AQI 101+; the fall peak was 126.
- ✓Cleanest month: October; worst month: September.
Frequently asked questions
What is the air quality like in New Haven in fall?▾
Across 2019–2025, the median daily AQI in New Haven in fall was 39 (Good). 72.7% of days were Good, 27.0% Moderate, and 0.3% reached Unhealthy for Sensitive Groups or worse, based on 637 monitored days in EPA's Air Quality System.
Is fall a good time for outdoor exercise in New Haven?▾
A typical fall day in New Haven sits in the Good range (median AQI 39), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Which pollutant causes New Haven's fall air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 59.7% of fall days in New Haven. The highest fall AQI recorded in 2019–2025 was 126 (Unhealthy for Sensitive Groups), in 2023.
New Haven fall air quality, year by year
New Haven fall air quality by year (New Haven-Milford, CT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 91 | 37 | 1 | 126 | PM2.5 |
| 2020 | 91 | 42 | 0 | 98 | PM2.5 |
| 2021 | 91 | 42 | 0 | 70 | PM2.5 |
| 2022 | 91 | 41 | 0 | 97 | PM2.5 |
| 2023worst | 91 | 42 | 1 | 101 | PM2.5 |
| 2024 | 91 | 37 | 0 | 69 | O3 |
| 2025cleanest | 91 | 36 | 0 | 97 | O3 |
What fall air means in New Haven
A typical fall day in New Haven sits in the Good range (median AQI 39), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Fall's median AQI of 39 is below New Haven's whole-year median of 44, making it one of the area's cleaner periods. Nationally, the median Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so New Haven runs in line with the national Fall norm; 0.3% of its Fall days topped AQI 100 versus 1.5% nationally (below average).
Within the season, October is the cleanest month (median AQI 37, 0.0% of days above 100) and September the worst (median 40, 1.0% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in New Haven
The latest EPA AirNow observation puts New Haven's AQI at 32 (O3). The figures above are multi-year season statistics, not today's reading.
View current New Haven air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (New Haven-Milford, CT), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.