Seattle Air Quality in 2019
In 2019, Seattle's air quality (Seattle-Tacoma-Bellevue, WA area) had a median daily AQI of 52 (Moderate) across 365 monitored days. 2 days (0.5%) reached Unhealthy for Sensitive Groups or worse, 168 were Good, and the year's peak AQI was 142 (Unhealthy for Sensitive Groups). Fine particulate matter (PM2.5) set the daily AQI on 282 of those days. The cleanest month of 2019 was June (median AQI 39, 0 days above 100) and the worst was January (median 60, 2 days above 100, peak 142).
- Good: 46.0%
- Moderate: 53.4%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.0%
Extra Protection for Seattle Homes
Air quality in Seattle is moderate (AQI 54), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
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How was Seattle's air quality in 2019?
Moderate on a typical day: median AQI 52, with 2 days above AQI 100 out of 365 monitored — the 2nd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2019: 142 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 282 days.
- ✓Cleanest month: June; worst: January.
Frequently asked questions
What was the average AQI in Seattle in 2019?▾
EPA's Air Quality System puts Seattle's (Seattle-Tacoma-Bellevue, WA) median daily AQI for 2019 at 52, which is Moderate. 2 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 142.
Which month had the worst air quality in Seattle in 2019?▾
The cleanest month of 2019 was June (median AQI 39, 0 days above 100) and the worst was January (median 60, 2 days above 100, peak 142).
Was 2019 a good or bad year for Seattle's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 2nd cleanest by days above AQI 100. 2019's median of 52 is above the area's typical annual median of 49.
Seattle month by month in 2019
Seattle air quality month by month, 2019 (Seattle-Tacoma-Bellevue, WA, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| Januaryworst | 31 | 60 | 2 | 142 | PM2.5 |
| February | 28 | 59 | 0 | 93 | PM2.5 |
| March | 31 | 56 | 0 | 93 | PM2.5 |
| April | 30 | 44 | 0 | 54 | O3 |
| May | 31 | 52 | 0 | 90 | PM2.5 |
| Junecleanest | 30 | 39 | 0 | 66 | PM2.5 |
| July | 31 | 40 | 0 | 80 | PM2.5 |
| August | 31 | 46 | 0 | 87 | PM2.5 |
| September | 30 | 39 | 0 | 57 | PM2.5 |
| October | 31 | 56 | 0 | 86 | PM2.5 |
| November | 30 | 63 | 0 | 94 | PM2.5 |
| December | 31 | 64 | 0 | 90 | PM2.5 |
How 2019 compares
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 2nd cleanest by days above AQI 100.
2019's median of 52 is above the area's typical annual median of 49.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Seattle
The latest EPA AirNow observation puts Seattle's AQI at 54 (PM2.5). The figures above are multi-year annual 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.