Seattle Air Quality in Spring
Across 2019–2025, Seattle's spring (March–May) air quality had a median AQI of 46 (Good) over 644 monitored days in the Seattle-Tacoma-Bellevue, WA area. 0.0% of spring days (0 of 644) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 54.8% of days. The cleanest spring on record here was 2022 (median AQI 44, 0 days above 100) and the worst was 2020 (median 51, 0 days above 100, peak AQI 81).
- Good: 65.7%
- Moderate: 34.3%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Seattle in spring?
Good on a typical day: median AQI 46 across 2019–2025, with 0.0% of spring days above AQI 100. Ground-level ozone is the main driver.
- ✓65.7% of spring days were Good (AQI 0–50), 34.3% Moderate (51–100).
- ✓0 days of 644 reached AQI 101+; the spring peak was 100.
- ✓Cleanest month: May; worst month: March.
Frequently asked questions
What is the air quality like in Seattle in spring?▾
Across 2019–2025, the median daily AQI in Seattle in spring was 46 (Good). 65.7% of days were Good, 34.3% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 644 monitored days in EPA's Air Quality System.
Is spring a good time for outdoor exercise in Seattle?▾
A typical spring day in Seattle sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of spring days reached AQI 101+ in 2019–2025.
Which pollutant causes Seattle's spring air quality problems?▾
Ground-level ozone set the daily AQI on 54.8% of spring days in Seattle. The highest spring AQI recorded in 2019–2025 was 100 (Moderate), in 2020.
Seattle spring air quality, year by year
Seattle spring air quality by year (Seattle-Tacoma-Bellevue, WA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 92 | 51 | 0 | 93 | PM2.5 |
| 2020worst | 92 | 51 | 0 | 81 | PM2.5 |
| 2021 | 92 | 48 | 0 | 80 | PM2.5 |
| 2022cleanest | 92 | 44 | 0 | 73 | O3 |
| 2023 | 92 | 46 | 0 | 77 | O3 |
| 2024 | 92 | 44 | 0 | 67 | O3 |
| 2025 | 92 | 45 | 0 | 100 | O3 |
What spring air means in Seattle
A typical spring day in Seattle sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of spring days reached AQI 101+ in 2019–2025.
Spring's median AQI of 46 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 Spring AQI across every EPA metro area (307,196 metro-days, 2019–2025) is 43, so Seattle runs in line with the national Spring norm; 0.0% of its Spring days topped AQI 100 versus 0.8% nationally (about the same).
Within the season, May is the cleanest month (median AQI 44, 0.0% of days above 100) and March the worst (median 49, 0.0% above 100).
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 season 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.