Boston Air Quality in April
Across 2019–2025, Boston's April air quality had a median AQI of 46 (Good) over 210 monitored days in the Boston-Cambridge-Newton, MA-NH area. 1.0% of April days (2 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 69.5% of days. The cleanest April on record here was 2019 (median AQI 45, 0 days above 100) and the worst was 2023 (median 52, 2 days above 100, peak AQI 119).
- Good: 69.0%
- Moderate: 30.0%
- Unhealthy for Sensitive Groups: 1.0%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Boston
Today's main pollutant in Boston is ground-level ozone (AQI 33). 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 Boston in April?
Good on a typical day: median AQI 46 across 2019–2025, with 1.0% of April days above AQI 100. Ground-level ozone is the main driver.
- ✓69.0% of April days were Good (AQI 0–50), 30.0% Moderate (51–100).
- ✓2 days of 210 reached AQI 101+; the April peak was 119.
- ✓Best April: 2019; worst April: 2023.
Frequently asked questions
What is the air quality like in Boston in April?▾
Across 2019–2025, the median daily AQI in Boston in April was 46 (Good). 69.0% of days were Good, 30.0% Moderate, and 1.0% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is April a good time for outdoor exercise in Boston?▾
A typical April day in Boston sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 100 of April days (1.0%) reached AQI 101+ in 2019–2025.
Which pollutant causes Boston's April air quality problems?▾
Ground-level ozone set the daily AQI on 69.5% of April days in Boston. The highest April AQI recorded in 2019–2025 was 119 (Unhealthy for Sensitive Groups), in 2023.
Boston April air quality, year by year
Boston April 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 |
|---|---|---|---|---|---|
| 2019cleanest | 30 | 45 | 0 | 69 | O3 |
| 2020 | 30 | 46 | 0 | 58 | O3 |
| 2021 | 30 | 45 | 0 | 74 | O3 |
| 2022 | 30 | 45 | 0 | 55 | O3 |
| 2023worst | 30 | 52 | 2 | 119 | O3 |
| 2024 | 30 | 45 | 0 | 58 | O3 |
| 2025 | 30 | 47 | 0 | 84 | O3 |
What April air means in Boston
A typical April day in Boston sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 100 of April days (1.0%) reached AQI 101+ in 2019–2025.
April's median AQI of 46 is in line with Boston's whole-year median of 48, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median April AQI across every EPA metro area (100,677 metro-days, 2019–2025) is 44, so Boston runs in line with the national April norm; 1.0% of its April days topped AQI 100 versus 0.7% nationally (about the same).
April is part of Boston's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Boston
The latest EPA AirNow observation puts Boston's AQI at 33 (O3). The figures above are multi-year month statistics, not today's reading.
View current Boston 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.