Worcester Air Quality in Fall
Across 2019–2025, Worcester's fall (September–November) air quality had a median AQI of 35 (Good) over 637 monitored days in the Worcester, MA-CT area. 0.2% of fall days (1 of 637) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 53.2% of days. The cleanest fall on record here was 2025 (median AQI 31, 0 days above 100) and the worst was 2023 (median 33, 1 day above 100, peak AQI 113).
- Good: 84.0%
- Moderate: 15.9%
- Unhealthy for Sensitive Groups: 0.2%
- 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 fall?
Good on a typical day: median AQI 35 across 2019–2025, with 0.2% of fall days above AQI 100. Ground-level ozone is the main driver.
- ✓84.0% of fall days were Good (AQI 0–50), 15.9% Moderate (51–100).
- ✓1 day of 637 reached AQI 101+; the fall peak was 113.
- ✓Cleanest month: November; worst month: October.
Frequently asked questions
What is the air quality like in Worcester in fall?▾
Across 2019–2025, the median daily AQI in Worcester in fall was 35 (Good). 84.0% of days were Good, 15.9% Moderate, and 0.2% reached Unhealthy for Sensitive Groups or worse, based on 637 monitored days in EPA's Air Quality System.
Is fall a good time for outdoor exercise in Worcester?▾
A typical fall day in Worcester sits in the Good range (median AQI 35), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Which pollutant causes Worcester's fall air quality problems?▾
Ground-level ozone set the daily AQI on 53.2% of fall days in Worcester. The highest fall AQI recorded in 2019–2025 was 113 (Unhealthy for Sensitive Groups), in 2023.
Worcester fall air quality, year by year
Worcester fall air quality by year (Worcester, MA-CT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 91 | 37 | 0 | 80 | PM2.5 |
| 2020 | 91 | 39 | 0 | 74 | PM2.5 |
| 2021 | 91 | 37 | 0 | 59 | PM2.5 |
| 2022 | 91 | 34 | 0 | 65 | PM2.5 |
| 2023worst | 91 | 33 | 1 | 113 | O3 |
| 2024 | 91 | 33 | 0 | 67 | O3 |
| 2025cleanest | 91 | 31 | 0 | 71 | O3 |
What fall air means in Worcester
A typical fall day in Worcester sits in the Good range (median AQI 35), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Fall's median AQI of 35 is below Worcester's whole-year median of 43, making it one of the area's cleaner periods. Nationally, the median Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so Worcester runs below the national Fall norm; 0.2% of its Fall days topped AQI 100 versus 1.5% nationally (below average).
Within the season, November is the cleanest month (median AQI 34, 0.0% of days above 100) and October the worst (median 34, 0.5% above 100).
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 season 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.