Santa Rosa Air Quality in Winter
Across 2019–2025, Santa Rosa's winter (December–February) air quality had a median AQI of 36 (Good) over 632 monitored days in the Santa Rosa, CA area. 0.0% of winter days (0 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 54.9% of days. The cleanest winter on record here was 2025 (median AQI 9, 0 days above 100) and the worst was 2022 (median 50, 0 days above 100, peak AQI 82).
- Good: 79.3%
- Moderate: 20.7%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Santa Rosa in winter?
Good on a typical day: median AQI 36 across 2019–2025, with 0.0% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓79.3% of winter days were Good (AQI 0–50), 20.7% Moderate (51–100).
- ✓0 days of 632 reached AQI 101+; the winter peak was 83.
- ✓Cleanest month: January; worst month: February.
Frequently asked questions
What is the air quality like in Santa Rosa in winter?▾
Across 2019–2025, the median daily AQI in Santa Rosa in winter was 36 (Good). 79.3% of days were Good, 20.7% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Santa Rosa?▾
A typical winter day in Santa Rosa sits in the Good range (median AQI 36), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Which pollutant causes Santa Rosa's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 54.9% of winter days in Santa Rosa. The highest winter AQI recorded in 2019–2025 was 83 (Moderate), in 2022.
Santa Rosa winter air quality, year by year
Santa Rosa winter air quality by year (Santa Rosa, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 90 | 37 | 0 | 83 | PM2.5 |
| 2020 | 91 | 40 | 0 | 66 | PM2.5 |
| 2021 | 90 | 38 | 0 | 71 | PM2.5 |
| 2022worst | 90 | 50 | 0 | 82 | PM2.5 |
| 2023 | 90 | 37 | 0 | 67 | PM2.5 |
| 2024 | 91 | 32 | 0 | 72 | O3 |
| 2025cleanest | 90 | 9 | 0 | 39 | PM10 |
What winter air means in Santa Rosa
A typical winter day in Santa Rosa sits in the Good range (median AQI 36), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Winter's median AQI of 36 is in line with Santa Rosa's whole-year median of 36, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Santa Rosa runs below the national Winter norm; 0.0% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, January is the cleanest month (median AQI 35, 0.0% of days above 100) and February the worst (median 36, 0.0% 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.