Santa Rosa Air Quality in Fall
Across 2019–2025, Santa Rosa's fall (September–November) air quality had a median AQI of 31 (Good) over 637 monitored days in the Santa Rosa, CA area. 1.4% of fall days (9 of 637) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 42.7% of days. The cleanest fall on record here was 2025 (median AQI 7, 0 days above 100) and the worst was 2020 (median 42, 7 days above 100, peak AQI 199).
- Good: 82.7%
- Moderate: 15.9%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.9%
Improve Indoor Air Quality
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How is the air in Santa Rosa in fall?
Good on a typical day: median AQI 31 across 2019–2025, with 1.4% of fall days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓82.7% of fall days were Good (AQI 0–50), 15.9% Moderate (51–100).
- ✓9 days of 637 reached AQI 101+; the fall peak was 199.
- ✓Cleanest month: November; worst month: September.
Frequently asked questions
What is the air quality like in Santa Rosa in fall?▾
Across 2019–2025, the median daily AQI in Santa Rosa in fall was 31 (Good). 82.7% of days were Good, 15.9% Moderate, and 1.4% 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 Santa Rosa?▾
A typical fall day in Santa Rosa sits in the Good range (median AQI 31), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 71 of fall days (1.4%) reached AQI 101+ in 2019–2025.
Which pollutant causes Santa Rosa's fall air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 42.7% of fall days in Santa Rosa. The highest fall AQI recorded in 2019–2025 was 199 (Unhealthy), in 2020.
Santa Rosa fall air quality, year by year
Santa Rosa fall air quality by year (Santa Rosa, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 91 | 35 | 0 | 86 | O3 |
| 2020worst | 91 | 42 | 7 | 199 | PM2.5 |
| 2021 | 91 | 38 | 0 | 77 | PM2.5 |
| 2022 | 91 | 33 | 0 | 68 | PM2.5 |
| 2023 | 91 | 31 | 2 | 117 | O3 |
| 2024 | 91 | 13 | 0 | 61 | PM2.5 |
| 2025cleanest | 91 | 7 | 0 | 22 | PM10 |
What fall air means in Santa Rosa
A typical fall day in Santa Rosa sits in the Good range (median AQI 31), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 71 of fall days (1.4%) reached AQI 101+ in 2019–2025.
Fall's median AQI of 31 is below Santa Rosa's whole-year median of 36, 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 Santa Rosa runs below the national Fall norm; 1.4% of its Fall days topped AQI 100 versus 1.5% nationally (about the same).
Within the season, November is the cleanest month (median AQI 33, 0.0% of days above 100) and September the worst (median 29, 3.4% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Santa Rosa
The latest EPA AirNow observation puts Santa Rosa's AQI at 36 (PM2.5). The figures above are multi-year season statistics, not today's reading.
View current Santa Rosa air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Santa Rosa, CA), 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.