Climate averages 1991–2020
Santa Rosa, United States weather
in December.
A cool, wet month: the coolest and the wettest of the year.
Long-term climate patterns, not a forecast for a particular trip.
December is a cool month in Santa Rosa, United States: daytime highs average 14.0°C and nights cool to about 4.2°C. By daytime temperature it is the coolest month of the year.
Expect about 150 mm of rain on roughly 10 days, which makes December a wet month (the wettest month of the year). Daylight, from sunrise to sunset, lasts about 9 h 33 min on an average December day.
The nearest other city in this atlas is Napa (41 km away). In December its highs average 14.2°C, about as warm as Santa Rosa, United States, with 110 mm of rain.
Among the 498 cities listed in the United States, Santa Rosa, United States ranks joint 163rd of 498 for the warmest December highs and 478th of 498 for the driest December (rainfall, lowest first). The mean December high of those 498 cities is 10.5°C; Santa Rosa, United States is 3.5°C warmer than that mean.
From December to January, average highs rise by 0.3°C to 14.4°C, and monthly rainfall falls from 150 mm to 145 mm.
The annual picture
December in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Santa Rosa, United States climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 14.4°C4.2°C | 4.2°C | 145 | 10.3 | 9.810 h |
| February | 15.7°C5.0°C | 5.0°C | 149 | 9.5 | 10.711 h |
| March | 17.5°C6.3°C | 6.3°C | 112 | 9.5 | 11.912 h |
| April | 19.8°C7.8°C | 7.8°C | 49 | 5.6 | 13.213 h |
| May | 23.6°C10.6°C | 10.6°C | 28 | 3.6 | 14.214 h |
| June | 27.8°C13.1°C | 13.1°C | 7.0 | 1.2 | 14.815 h |
| July | 29.6°C14.1°C | 14.1°C | 0.4 | 0.1 | 14.615 h |
| August | 29.5°C14.3°C | 14.3°C | 1.1 | 0.2 | 13.714 h |
| September | 28.4°C13.6°C | 13.6°C | 3.1 | 0.6 | 12.512 h |
| October | 24.4°C11.2°C | 11.2°C | 34 | 3.2 | 11.211 h |
| November | 18.0°C7.0°C | 7.0°C | 75 | 6.2 | 10.110 h |
| December, selected | 14.0°C4.2°C | 4.2°C | 150 | 10.2 | 9.510 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
December in nearby cities
- Napa in DecemberUnited States · 41 kmHigh 14.2°C · Low 5.6°C · 110 mm rain
- Vallejo in DecemberUnited States · 55 kmHigh 13.9°C · Low 5.5°C · 95 mm rain
- Fairfield in DecemberUnited States · 63 kmHigh 13.6°C · Low 5.8°C · 101 mm rain
- Vacaville in DecemberUnited States · 64 kmHigh 13.8°C · Low 5.8°C · 101 mm rain
- Berkeley in DecemberUnited States · 74 kmHigh 13.6°C · Low 5.7°C · 87 mm rain
- San Francisco in DecemberUnited States · 78 kmHigh 13.5°C · Low 6.3°C · 108 mm rain
- Concord (California), United States in DecemberUnited States · 79 kmHigh 13.8°C · Low 6.0°C · 84 mm rain
- Oakland in DecemberUnited States · 81 kmHigh 13.8°C · Low 6.0°C · 87 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Santa Rosa) is explained once on the Santa Rosa, United States year overview and on the Sources, method and limits page.