Tacoma Air Quality in September
Across 2019–2025, Tacoma's September air quality had a median AQI of 48 (Good) over 210 monitored days in the Seattle-Tacoma-Bellevue, WA area. 8.1% of September days (17 of 210) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 80.5% of days. The cleanest September on record here was 2019 (median AQI 39, 0 days above 100) and the worst was 2020 (median 54, 11 days above 100, peak AQI 299).
- Good: 54.3%
- Moderate: 37.6%
- Unhealthy for Sensitive Groups: 2.9%
- Unhealthy or worse: 5.2%
Improve Indoor Air Quality
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How is the air in Tacoma in September?
Good on a typical day: median AQI 48 across 2019–2025, with 8.1% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓54.3% of September days were Good (AQI 0–50), 37.6% Moderate (51–100).
- ✓17 days of 210 reached AQI 101+; the September peak was 299.
- ✓Best September: 2019; worst September: 2020.
Frequently asked questions
What is the air quality like in Tacoma in September?▾
Across 2019–2025, the median daily AQI in Tacoma in September was 48 (Good). 54.3% of days were Good, 37.6% Moderate, and 8.1% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in Tacoma?▾
A typical September day in Tacoma sits in the Good range (median AQI 48), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 12 of September days (8.1%) reached AQI 101+ in 2019–2025.
Which pollutant causes Tacoma's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 80.5% of September days in Tacoma. The highest September AQI recorded in 2019–2025 was 299 (Very Unhealthy), in 2020.
Tacoma September air quality, year by year
Tacoma September air quality by year (Seattle-Tacoma-Bellevue, WA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 30 | 39 | 0 | 57 | PM2.5 |
| 2020worst | 30 | 54 | 11 | 299 | PM2.5 |
| 2021 | 30 | 44 | 0 | 87 | O3 |
| 2022 | 30 | 55 | 5 | 160 | PM2.5 |
| 2023 | 30 | 47 | 0 | 71 | PM2.5 |
| 2024 | 30 | 48 | 0 | 76 | PM2.5 |
| 2025 | 30 | 53 | 1 | 125 | PM2.5 |
What September air means in Tacoma
A typical September day in Tacoma sits in the Good range (median AQI 48), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 12 of September days (8.1%) reached AQI 101+ in 2019–2025.
September's median AQI of 48 is in line with Tacoma's whole-year median of 49, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Tacoma runs above the national September norm; 8.1% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Tacoma's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Tacoma
The latest EPA AirNow observation puts Tacoma's AQI at 41 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Tacoma 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.