Cambridge Air Quality in January
Across 2019–2025, Cambridge's January air quality had a median AQI of 49 (Good) over 217 monitored days in the Boston-Cambridge-Newton, MA-NH area. 0.0% of January days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 77.4% of days. The cleanest January on record here was 2021 (median AQI 43, 0 days above 100) and the worst was 2022 (median 55, 0 days above 100, peak AQI 72).
- Good: 51.6%
- Moderate: 48.4%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Cambridge in January?
Good on a typical day: median AQI 49 across 2019–2025, with 0.0% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓51.6% of January days were Good (AQI 0–50), 48.4% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the January peak was 89.
- ✓Best January: 2021; worst January: 2022.
Frequently asked questions
What is the air quality like in Cambridge in January?▾
Across 2019–2025, the median daily AQI in Cambridge in January was 49 (Good). 51.6% of days were Good, 48.4% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is January a good time for outdoor exercise in Cambridge?▾
A typical January day in Cambridge sits in the Good range (median AQI 49), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of January days reached AQI 101+ in 2019–2025.
Which pollutant causes Cambridge's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 77.4% of January days in Cambridge. The highest January AQI recorded in 2019–2025 was 89 (Moderate), in 2022.
Cambridge January air quality, year by year
Cambridge January air quality by year (Boston-Cambridge-Newton, MA-NH, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 53 | 0 | 66 | PM2.5 |
| 2020 | 31 | 46 | 0 | 71 | PM2.5 |
| 2021cleanest | 31 | 43 | 0 | 89 | PM2.5 |
| 2022worst | 31 | 55 | 0 | 72 | PM2.5 |
| 2023 | 31 | 49 | 0 | 65 | PM2.5 |
| 2024 | 31 | 43 | 0 | 63 | PM2.5 |
| 2025 | 31 | 43 | 0 | 65 | PM2.5 |
What January air means in Cambridge
A typical January day in Cambridge sits in the Good range (median AQI 49), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of January days reached AQI 101+ in 2019–2025.
January's median AQI of 49 is in line with Cambridge's whole-year median of 48, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median January AQI across every EPA metro area (95,602 metro-days, 2019–2025) is 39, so Cambridge runs above the national January norm; 0.0% of its January days topped AQI 100 versus 0.7% nationally (about the same).
January is part of Cambridge's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Cambridge
The latest EPA AirNow observation puts Cambridge's AQI at 33 (O3). The figures above are multi-year month statistics, not today's reading.
View current Cambridge air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Boston-Cambridge-Newton, MA-NH), 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.