Santa Rosa Air Quality in December
Across 2019–2025, Santa Rosa's December air quality had a median AQI of 36 (Good) over 217 monitored days in the Santa Rosa, CA area. 0.0% of December days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 68.7% of days. The cleanest December 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: 70.5%
- Moderate: 29.5%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Santa Rosa in December?
Good on a typical day: median AQI 36 across 2019–2025, with 0.0% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓70.5% of December days were Good (AQI 0–50), 29.5% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the December peak was 82.
- ✓Best December: 2025; worst December: 2022.
Frequently asked questions
What is the air quality like in Santa Rosa in December?▾
Across 2019–2025, the median daily AQI in Santa Rosa in December was 36 (Good). 70.5% of days were Good, 29.5% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Santa Rosa?▾
A typical December 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 December days reached AQI 101+ in 2019–2025.
Which pollutant causes Santa Rosa's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 68.7% of December days in Santa Rosa. The highest December AQI recorded in 2019–2025 was 82 (Moderate), in 2022.
Santa Rosa December air quality, year by year
Santa Rosa December air quality by year (Santa Rosa, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 38 | 0 | 56 | PM2.5 |
| 2020 | 31 | 48 | 0 | 66 | PM2.5 |
| 2021 | 31 | 41 | 0 | 66 | PM2.5 |
| 2022worst | 31 | 50 | 0 | 82 | PM2.5 |
| 2023 | 31 | 35 | 0 | 67 | PM2.5 |
| 2024 | 31 | 34 | 0 | 72 | PM2.5 |
| 2025cleanest | 31 | 9 | 0 | 17 | PM10 |
What December air means in Santa Rosa
A typical December 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 December days reached AQI 101+ in 2019–2025.
December'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 December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Santa Rosa runs in line with the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Santa Rosa's winter season (December, January, February); the winter page pools all three months.
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 month 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.