Worcester Air Quality in Winter
Across 2019–2025, Worcester's winter (December–February) air quality had a median AQI of 42 (Good) over 632 monitored days in the Worcester, MA-CT area. 0.0% of winter days (0 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 63.0% of days. The cleanest winter on record here was 2024 (median AQI 36, 0 days above 100) and the worst was 2021 (median 51, 0 days above 100, peak AQI 88).
- Good: 67.6%
- Moderate: 32.4%
- 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 winter?
Good on a typical day: median AQI 42 across 2019–2025, with 0.0% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓67.6% of winter days were Good (AQI 0–50), 32.4% Moderate (51–100).
- ✓0 days of 632 reached AQI 101+; the winter peak was 88.
- ✓Cleanest month: December; worst month: February.
Frequently asked questions
What is the air quality like in Worcester in winter?▾
Across 2019–2025, the median daily AQI in Worcester in winter was 42 (Good). 67.6% of days were Good, 32.4% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Worcester?▾
A typical winter day in Worcester sits in the Good range (median AQI 42), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Which pollutant causes Worcester's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 63.0% of winter days in Worcester. The highest winter AQI recorded in 2019–2025 was 88 (Moderate), in 2021.
Worcester winter air quality, year by year
Worcester winter air quality by year (Worcester, MA-CT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 90 | 48 | 0 | 80 | PM2.5 |
| 2020 | 91 | 43 | 0 | 68 | PM2.5 |
| 2021worst | 90 | 51 | 0 | 88 | PM2.5 |
| 2022 | 90 | 48 | 0 | 73 | PM2.5 |
| 2023 | 90 | 37 | 0 | 63 | PM2.5 |
| 2024cleanest | 91 | 36 | 0 | 63 | O3 |
| 2025 | 90 | 38 | 0 | 73 | O3 |
What winter air means in Worcester
A typical winter day in Worcester sits in the Good range (median AQI 42), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Winter's median AQI of 42 is in line with Worcester's whole-year median of 43, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Worcester runs in line with the national Winter norm; 0.0% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, December is the cleanest month (median AQI 37, 0.0% of days above 100) and February the worst (median 47, 0.0% 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.