Seattle Air Quality in March
Across 2019–2025, Seattle's March air quality had a median AQI of 49 (Good) over 217 monitored days in the Seattle-Tacoma-Bellevue, WA area. 0.0% of March days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 58.5% of days. The cleanest March on record here was 2022 (median AQI 44, 0 days above 100) and the worst was 2019 (median 56, 0 days above 100, peak AQI 93).
- Good: 52.5%
- Moderate: 47.5%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Seattle in March?
Good on a typical day: median AQI 49 across 2019–2025, with 0.0% of March days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓52.5% of March days were Good (AQI 0–50), 47.5% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the March peak was 93.
- ✓Best March: 2022; worst March: 2019.
Frequently asked questions
What is the air quality like in Seattle in March?▾
Across 2019–2025, the median daily AQI in Seattle in March was 49 (Good). 52.5% of days were Good, 47.5% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is March a good time for outdoor exercise in Seattle?▾
A typical March day in Seattle 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 March days reached AQI 101+ in 2019–2025.
Which pollutant causes Seattle's March air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 58.5% of March days in Seattle. The highest March AQI recorded in 2019–2025 was 93 (Moderate), in 2019.
Seattle March air quality, year by year
Seattle March air quality by year (Seattle-Tacoma-Bellevue, WA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 31 | 56 | 0 | 93 | PM2.5 |
| 2020 | 31 | 52 | 0 | 81 | PM2.5 |
| 2021 | 31 | 55 | 0 | 80 | PM2.5 |
| 2022cleanest | 31 | 44 | 0 | 73 | O3 |
| 2023 | 31 | 47 | 0 | 77 | PM2.5 |
| 2024 | 31 | 46 | 0 | 67 | PM2.5 |
| 2025 | 31 | 44 | 0 | 66 | O3 |
What March air means in Seattle
A typical March day in Seattle 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 March days reached AQI 101+ in 2019–2025.
March's median AQI of 49 is in line with Seattle's whole-year median of 49, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median March AQI across every EPA metro area (102,455 metro-days, 2019–2025) is 42, so Seattle runs above the national March norm; 0.0% of its March days topped AQI 100 versus 0.4% nationally (about the same).
March is part of Seattle's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Seattle
The latest EPA AirNow observation puts Seattle's AQI at 37 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Seattle air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Seattle-Tacoma-Bellevue, WA), 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.