Spokane Air Quality in September
Across 2019–2025, Spokane's September air quality had a median AQI of 45 (Good) over 210 monitored days in the Spokane-Spokane Valley, WA area. 11.9% of September days (25 of 210) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 53.3% of days. The cleanest September on record here was 2019 (median AQI 33, 0 days above 100) and the worst was 2025 (median 72, 9 days above 100, peak AQI 243).
- Good: 56.7%
- Moderate: 31.4%
- Unhealthy for Sensitive Groups: 3.8%
- Unhealthy or worse: 8.1%
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How is the air in Spokane in September?
Good on a typical day: median AQI 45 across 2019–2025, with 11.9% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓56.7% of September days were Good (AQI 0–50), 31.4% Moderate (51–100).
- ✓25 days of 210 reached AQI 101+; the September peak was 957.
- ✓Best September: 2019; worst September: 2025.
Frequently asked questions
What is the air quality like in Spokane in September?▾
Across 2019–2025, the median daily AQI in Spokane in September was 45 (Good). 56.7% of days were Good, 31.4% Moderate, and 11.9% 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 Spokane?▾
A typical September day in Spokane sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 8 of September days (11.9%) reached AQI 101+ in 2019–2025.
Which pollutant causes Spokane's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 53.3% of September days in Spokane. The highest September AQI recorded in 2019–2025 was 957 (Hazardous), in 2025.
Spokane September air quality, year by year
Spokane September air quality by year (Spokane-Spokane Valley, WA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 30 | 33 | 0 | 67 | O3 |
| 2020 | 30 | 57 | 9 | 957 | PM2.5 |
| 2021 | 30 | 42 | 2 | 117 | O3 |
| 2022 | 30 | 59 | 5 | 185 | PM2.5 |
| 2023 | 30 | 41 | 0 | 68 | O3 |
| 2024 | 30 | 39 | 0 | 85 | O3 |
| 2025worst | 30 | 72 | 9 | 243 | PM2.5 |
What September air means in Spokane
A typical September day in Spokane sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 8 of September days (11.9%) reached AQI 101+ in 2019–2025.
September's median AQI of 45 is in line with Spokane's whole-year median of 47, 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 Spokane runs in line with the national September norm; 11.9% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Spokane's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Spokane
The latest EPA AirNow observation puts Spokane's AQI at 26 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Spokane air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Spokane-Spokane Valley, 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.