New Haven Air Quality in Winter
Across 2019–2025, New Haven's winter (December–February) air quality had a median AQI of 43 (Good) over 632 monitored days in the New Haven-Milford, CT area. 0.2% of winter days (1 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 70.6% of days. The cleanest winter on record here was 2025 (median AQI 37, 0 days above 100) and the worst was 2019 (median 44, 1 day above 100, peak AQI 105).
- Good: 60.1%
- Moderate: 39.7%
- Unhealthy for Sensitive Groups: 0.2%
- 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.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
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How is the air in New Haven in winter?
Good on a typical day: median AQI 43 across 2019–2025, with 0.2% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓60.1% of winter days were Good (AQI 0–50), 39.7% Moderate (51–100).
- ✓1 day of 632 reached AQI 101+; the winter peak was 105.
- ✓Cleanest month: January; worst month: February.
Frequently asked questions
What is the air quality like in New Haven in winter?▾
Across 2019–2025, the median daily AQI in New Haven in winter was 43 (Good). 60.1% of days were Good, 39.7% Moderate, and 0.2% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in New Haven?▾
A typical winter day in New Haven sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Which pollutant causes New Haven's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 70.6% of winter days in New Haven. The highest winter AQI recorded in 2019–2025 was 105 (Unhealthy for Sensitive Groups), in 2019.
New Haven winter air quality, year by year
New Haven winter air quality by year (New Haven-Milford, CT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 90 | 44 | 1 | 105 | PM2.5 |
| 2020 | 91 | 50 | 0 | 96 | PM2.5 |
| 2021 | 90 | 49 | 0 | 95 | PM2.5 |
| 2022 | 90 | 46 | 0 | 87 | PM2.5 |
| 2023 | 90 | 43 | 0 | 83 | PM2.5 |
| 2024 | 91 | 39 | 0 | 70 | PM2.5 |
| 2025cleanest | 90 | 37 | 0 | 71 | O3 |
What winter air means in New Haven
A typical winter day in New Haven sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Winter's median AQI of 43 is in line with New Haven's whole-year median of 44, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so New Haven runs in line with the national Winter norm; 0.2% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, January is the cleanest month (median AQI 41, 0.0% of days above 100) and February the worst (median 44, 0.5% 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.