New Haven Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for New Haven (New Haven-Milford, CT area) was June 7, 2023, when the daily AQI reached 208 (Very Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 10 of the 10 worst days were Unhealthy (AQI 151+) or worse; 6 of the 10 were driven by ground-level ozone and 4 by fine particulate matter (PM2.5), and 3 of them fell in 2023. The cleanest day was March 8, 2020 at AQI 2 (Good); the 10 best days span 6 different years.
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
As an Amazon Associate, we earn from qualifying purchases.
When were New Haven's worst and best air quality days?
Worst: June 7, 2023, AQI 208 (Very Unhealthy, PM2.5). Best: March 8, 2020, AQI 2 (Good). Based on 2,557 EPA-monitored days in the New Haven-Milford, CT area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 152 (Unhealthy).
- ✓Ground-level ozone drove 6 of the 10 worst days.
- ✓2023 accounts for 3 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in New Haven?▾
June 7, 2023: the New Haven-Milford, CT area's daily AQI hit 208 (Very Unhealthy), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in New Haven?▾
March 8, 2020, with a daily AQI of 2 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was New Haven's worst air quality day in 2025?▾
July 29, 2025, AQI 159 (Unhealthy), set by ground-level ozone, in peak ozone season.
Which pollutant causes New Haven's worst air days?▾
Ground-level ozone set the AQI on 6 of the 10 worst days; fine particulate matter (PM2.5) on 4. The tables above list the defining pollutant for every day.
New Haven's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the New Haven-Milford, CT area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 208 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2020 page) | 174 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 3 | (2023 page) | 172 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2023 page) | 160 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2025 page) | 159 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 6 | (2021 page) | 159 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 7 | (2019 page) | 159 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 8 | (2024 page) | 156 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 9 | (2020 page) | 156 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 10 | (2021 page) | 152 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Worst day of each year in New Haven
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 159 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 174 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2021 | 159 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2022 | 133 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 208 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 156 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 159 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
New Haven's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the New Haven-Milford, CT area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2020 page) | 2 | Good | CO — carbon monoxide |
| 2 | (2022 page) | 11 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2023 page) | 16 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2024 page) | 17 | Good | O3 — ground-level ozone |
| 5 | (2023 page) | 17 | Good | O3 — ground-level ozone |
| 6 | (2022 page) | 17 | Good | NO2 — nitrogen dioxide |
| 7 | (2021 page) | 17 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2023 page) | 18 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2019 page) | 18 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2022 page) | 19 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in New Haven
The latest EPA AirNow observation puts New Haven's AQI at 32 (O3). The days above are historical records, 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.