Worcester, Massachusetts Air Quality
Worcester air quality today — the AQI, the main pollutant, and whether it’s safe to exercise outside right now
Worcester, MA · Air quality right now
The air quality index in Worcester, MA is 28 (Good) right now — safe for outdoor activity.
Is it safe to be outside in Worcester today?
AQI 28 Yes — air quality is Good
Air is clean — great for outdoor activity.Main pollutant: PM2.5Observed 12:00 AM EDT
Pollutants right now
- PM2.52.1 µg/m³Main pollutantfine particles — smoke, exhaust, soot
- PM102.3 µg/m³coarse particles — dust, pollen, ash
- Ozone41 µg/m³smog — builds on hot, sunny days
- NO₂13 µg/m³nitrogen dioxide — traffic, combustion
ExerciseOK to run — no air-quality limits on outdoor exercise.
How to read Worcester’s air quality
Guides: The AQI Scale, Explained · Air Quality Alerts, Decoded · How to Read a Wildfire Smoke Map · Why Wildfire Smoke Travels 1,000 Miles.
Air quality over time in Worcester
Across the EPA’s county records from 2020 to 2025, Worcester’s cleanest year was 2024 (median AQI 37) and its most polluted was 2021 (median AQI 45); the typical (median) day has trended cleaner since 2020.
| Year | Median AQI | Unhealthy+ | Main pollutant | USG | Moderate | Good |
|---|---|---|---|---|---|---|
| 2020 | 43 | 0 | PM2.5 | 0 | 109 | 257 |
| 2021 | 45 | 0 | PM2.5 | 3 | 144 | 218 |
| 2022 | 45 | 0 | PM2.5 | 0 | 137 | 228 |
| 2023 | 39 | 0 | Ozone | 4 | 93 | 268 |
| 2024 | 37 | 0 | Ozone | 0 | 45 | 321 |
| 2025 | 39 | 0 | Ozone | 0 | 67 | 298 |
“USG” is Unhealthy for Sensitive Groups (AQI 101–150); “Unhealthy+” combines the Unhealthy, Very Unhealthy, and Hazardous days. In 2024 the EPA tightened the annual fine-particle (PM2.5) standard to 9 µg/m³ from the previous 12 µg/m³, so counties near the old limit read worse against the new one. Source: EPA AQS annual summaries, 2020–2025.
Frequently asked
- What was the worst year for air quality in Worcester?
- In the EPA's 2020–2025 county records, 2023 had the most days above AQI 100: 4 days (4 Unhealthy for Sensitive Groups, 0 Unhealthy or worse). The highest median AQI came in 2021 (45; 2023's was 39).
- How many unhealthy air days does Worcester have?
- Across 2020–2025, under 1% of the days reported for Worcester's county had an AQI above 100 (7 of 2192), about 1 day a year. 2025 had 0 days.
- What's the main air pollutant in Worcester?
- PM2.5 drove Worcester's county AQI on the most days in 3 of 6 years (2020–2025); Ozone in 2023, 2024, 2025.