Worcester Air Quality in September
Across 2019–2025, Worcester's September air quality had a median AQI of 37 (Good) over 210 monitored days in the Worcester, MA-CT area. 0.0% of September days (0 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 54.8% of days. The cleanest September on record here was 2022 (median AQI 31, 0 days above 100) and the worst was 2021 (median 40, 0 days above 100, peak AQI 58).
- Good: 84.8%
- Moderate: 15.2%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Worcester
Today's main pollutant in Worcester 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 Worcester in September?
Good on a typical day: median AQI 37 across 2019–2025, with 0.0% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓84.8% of September days were Good (AQI 0–50), 15.2% Moderate (51–100).
- ✓0 days of 210 reached AQI 101+; the September peak was 86.
- ✓Best September: 2022; worst September: 2021.
Frequently asked questions
What is the air quality like in Worcester in September?▾
Across 2019–2025, the median daily AQI in Worcester in September was 37 (Good). 84.8% of days were Good, 15.2% Moderate, and 0.0% 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 Worcester?▾
A typical September day in Worcester 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 September days reached AQI 101+ in 2019–2025.
Which pollutant causes Worcester's September air quality problems?▾
Ground-level ozone set the daily AQI on 54.8% of September days in Worcester. The highest September AQI recorded in 2019–2025 was 86 (Moderate), in 2021.
Worcester September air quality, year by year
Worcester September air quality by year (Worcester, MA-CT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 39 | 0 | 80 | PM2.5 |
| 2020 | 30 | 37 | 0 | 74 | PM2.5 |
| 2021worst | 30 | 40 | 0 | 58 | PM2.5 |
| 2022cleanest | 30 | 31 | 0 | 58 | O3 |
| 2023 | 30 | 38 | 0 | 86 | O3 |
| 2024 | 30 | 35 | 0 | 58 | O3 |
| 2025 | 30 | 36 | 0 | 49 | O3 |
What September air means in Worcester
A typical September day in Worcester 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 September days reached AQI 101+ in 2019–2025.
September's median AQI of 37 is below Worcester'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 Worcester runs below the national September norm; 0.0% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Worcester's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Worcester
The latest EPA AirNow observation puts Worcester's AQI at 32 (O3). The figures above are multi-year month statistics, not today's reading.
View current Worcester air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Worcester, MA-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.