New Haven Air Quality in October
Across 2019–2025, New Haven's October air quality had a median AQI of 37 (Good) over 217 monitored days in the New Haven-Milford, CT area. 0.0% of October days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 67.7% of days. The cleanest October on record here was 2025 (median AQI 31, 0 days above 100) and the worst was 2020 (median 43, 0 days above 100, peak AQI 60).
- Good: 73.3%
- Moderate: 26.7%
- Unhealthy for Sensitive Groups: 0.0%
- 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 October?
Good on a typical day: median AQI 37 across 2019–2025, with 0.0% of October days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓73.3% of October days were Good (AQI 0–50), 26.7% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the October peak was 89.
- ✓Best October: 2025; worst October: 2020.
Frequently asked questions
What is the air quality like in New Haven in October?▾
Across 2019–2025, the median daily AQI in New Haven in October was 37 (Good). 73.3% of days were Good, 26.7% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is October a good time for outdoor exercise in New Haven?▾
A typical October day in New Haven sits in the Good range (median AQI 37), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of October days reached AQI 101+ in 2019–2025.
Which pollutant causes New Haven's October air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 67.7% of October days in New Haven. The highest October AQI recorded in 2019–2025 was 89 (Moderate), in 2020.
New Haven October air quality, year by year
New Haven October 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 | 31 | 35 | 0 | 54 | PM2.5 |
| 2020worst | 31 | 43 | 0 | 60 | PM2.5 |
| 2021 | 31 | 39 | 0 | 54 | PM2.5 |
| 2022 | 31 | 41 | 0 | 66 | PM2.5 |
| 2023 | 31 | 39 | 0 | 89 | PM2.5 |
| 2024 | 31 | 37 | 0 | 69 | PM2.5 |
| 2025cleanest | 31 | 31 | 0 | 80 | O3 |
What October air means in New Haven
A typical October day in New Haven sits in the Good range (median AQI 37), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of October days reached AQI 101+ in 2019–2025.
October's median AQI of 37 is below New Haven's whole-year median of 44, making it one of the area's cleaner periods. Nationally, the median October AQI across every EPA metro area (102,872 metro-days, 2019–2025) is 38, so New Haven runs in line with the national October norm; 0.0% of its October days topped AQI 100 versus 1.3% nationally (below average).
October is part of New Haven's fall season (September, October, November); the fall page pools all three months.
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 month 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.