Washington Air Quality in Fall
Across 2019–2025, Washington's fall (September–November) air quality had a median AQI of 47 (Good) over 637 monitored days in the Washington-Arlington-Alexandria, DC-VA-MD-WV area. 0.2% of fall days (1 of 637) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 63.4% of days. The cleanest fall on record here was 2024 (median AQI 42, 0 days above 100) and the worst was 2019 (median 49, 1 day above 100, peak AQI 112).
- Good: 59.7%
- Moderate: 40.2%
- Unhealthy for Sensitive Groups: 0.2%
- Unhealthy or worse: 0.0%
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How is the air in Washington in fall?
Good on a typical day: median AQI 47 across 2019–2025, with 0.2% of fall days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓59.7% of fall days were Good (AQI 0–50), 40.2% Moderate (51–100).
- ✓1 day of 637 reached AQI 101+; the fall peak was 112.
- ✓Cleanest month: October; worst month: September.
Frequently asked questions
What is the air quality like in Washington in fall?▾
Across 2019–2025, the median daily AQI in Washington in fall was 47 (Good). 59.7% of days were Good, 40.2% Moderate, and 0.2% reached Unhealthy for Sensitive Groups or worse, based on 637 monitored days in EPA's Air Quality System.
Is fall a good time for outdoor exercise in Washington?▾
A typical fall day in Washington sits in the Good range (median AQI 47), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Which pollutant causes Washington's fall air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 63.4% of fall days in Washington. The highest fall AQI recorded in 2019–2025 was 112 (Unhealthy for Sensitive Groups), in 2019.
Washington fall air quality, year by year
Washington fall air quality by year (Washington-Arlington-Alexandria, DC-VA-MD-WV, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 91 | 49 | 1 | 112 | PM2.5 |
| 2020 | 91 | 48 | 0 | 90 | PM2.5 |
| 2021 | 91 | 48 | 0 | 73 | PM2.5 |
| 2022 | 91 | 47 | 0 | 80 | PM2.5 |
| 2023 | 91 | 47 | 0 | 84 | PM2.5 |
| 2024cleanest | 91 | 42 | 0 | 87 | PM2.5 |
| 2025 | 91 | 43 | 0 | 90 | O3 |
What fall air means in Washington
A typical fall day in Washington sits in the Good range (median AQI 47), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Fall's median AQI of 47 is below Washington's whole-year median of 52, making it one of the area's cleaner periods. Nationally, the median Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so Washington runs above the national Fall norm; 0.2% of its Fall days topped AQI 100 versus 1.5% nationally (below average).
Within the season, October is the cleanest month (median AQI 43, 0.0% of days above 100) and September the worst (median 48, 0.5% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Washington
The latest EPA AirNow observation puts Washington's AQI at 41 (PM2.5). The figures above are multi-year season statistics, not today's reading.
View current Washington air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Washington-Arlington-Alexandria, DC-VA-MD-WV), 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.