Hartford Air Quality in September
Across 2019–2025, Hartford's September air quality had a median AQI of 37 (Good) over 210 monitored days in the Hartford-West Hartford-East Hartford, CT area. 1.0% of September days (2 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 58.6% of days. The cleanest September on record here was 2024 (median AQI 34, 0 days above 100) and the worst was 2019 (median 34, 2 days above 100, peak AQI 122).
- Good: 82.4%
- Moderate: 16.7%
- Unhealthy for Sensitive Groups: 1.0%
- Unhealthy or worse: 0.0%
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How is the air in Hartford in September?
Good on a typical day: median AQI 37 across 2019–2025, with 1.0% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓82.4% of September days were Good (AQI 0–50), 16.7% Moderate (51–100).
- ✓2 days of 210 reached AQI 101+; the September peak was 122.
- ✓Best September: 2024; worst September: 2019.
Frequently asked questions
What is the air quality like in Hartford in September?▾
Across 2019–2025, the median daily AQI in Hartford in September was 37 (Good). 82.4% of days were Good, 16.7% Moderate, and 1.0% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in Hartford?▾
A typical September day in Hartford sits in the Good range (median AQI 37), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 100 of September days (1.0%) reached AQI 101+ in 2019–2025.
Which pollutant causes Hartford's September air quality problems?▾
Ground-level ozone set the daily AQI on 58.6% of September days in Hartford. The highest September AQI recorded in 2019–2025 was 122 (Unhealthy for Sensitive Groups), in 2019.
Hartford September air quality, year by year
Hartford September air quality by year (Hartford-West Hartford-East Hartford, CT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 30 | 34 | 2 | 122 | O3 |
| 2020 | 30 | 36 | 0 | 84 | O3 |
| 2021 | 30 | 40 | 0 | 74 | PM2.5 |
| 2022 | 30 | 35 | 0 | 87 | O3 |
| 2023 | 30 | 44 | 0 | 98 | PM2.5 |
| 2024cleanest | 30 | 34 | 0 | 93 | O3 |
| 2025 | 30 | 42 | 0 | 64 | O3 |
What September air means in Hartford
A typical September day in Hartford sits in the Good range (median AQI 37), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 100 of September days (1.0%) reached AQI 101+ in 2019–2025.
September's median AQI of 37 is below Hartford's whole-year median of 43, making it one of the area's cleaner periods. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Hartford runs below the national September norm; 1.0% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Hartford's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Hartford
The latest EPA AirNow observation puts Hartford's AQI at 36 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Hartford air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Hartford-West Hartford-East Hartford, 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.