Climate averages 1991–2020
Vallejo weather
in December.
A cool, wet month: the coolest and the 10th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
December is a cool month in Vallejo: daytime highs average 13.9°C and nights cool to about 5.5°C. By daytime temperature it is the coolest month of the year.
Expect about 95 mm of rain on roughly 9 days, which makes December a wet month (the 10th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 9 h 34 min on an average December day.
The nearest other city in this atlas is Napa (22 km away). In December its highs average 14.2°C, about as warm as Vallejo, with 110 mm of rain.
Among the 498 cities listed in the United States, Vallejo ranks joint 171st of 498 for the warmest December highs and joint 354th of 498 for the driest December (rainfall, lowest first). The mean December high of those 498 cities is 10.5°C; Vallejo is 3.3°C warmer than that mean.
From December to January, average highs rise by 0.1°C to 14.0°C, and monthly rainfall rises from 95 mm to 101 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
Vallejo climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 14.0°C5.1°C | 5.1°C | 101 | 9.3 | 9.810 h |
| February | 15.6°C6.1°C | 6.1°C | 107 | 8.9 | 10.811 h |
| March | 17.7°C7.3°C | 7.3°C | 80 | 8.7 | 11.912 h |
| April | 20.3°C8.5°C | 8.5°C | 37 | 4.9 | 13.213 h |
| May | 23.7°C10.7°C | 10.7°C | 19 | 3.0 | 14.214 h |
| June | 27.4°C12.6°C | 12.6°C | 4.2 | 0.8 | 14.815 h |
| July | 28.5°C13.4°C | 13.4°C | 0.5 | 0.1 | 14.515 h |
| August | 28.6°C13.8°C | 13.8°C | 0.9 | 0.2 | 13.614 h |
| September | 28.2°C13.5°C | 13.5°C | 1.8 | 0.4 | 12.512 h |
| October | 24.4°C11.9°C | 11.9°C | 23 | 3.0 | 11.211 h |
| November | 18.0°C8.3°C | 8.3°C | 49 | 5.6 | 10.210 h |
| December, selected | 13.9°C5.5°C | 5.5°C | 95 | 9.3 | 9.610 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 · 22 kmHigh 14.2°C · Low 5.6°C · 110 mm rain
- Concord (California), United States in DecemberUnited States · 24 kmHigh 13.8°C · Low 6.0°C · 84 mm rain
- Fairfield in DecemberUnited States · 25 kmHigh 13.6°C · Low 5.8°C · 101 mm rain
- Berkeley in DecemberUnited States · 26 kmHigh 13.6°C · Low 5.7°C · 87 mm rain
- Oakland in DecemberUnited States · 33 kmHigh 13.8°C · Low 6.0°C · 87 mm rain
- Vacaville in DecemberUnited States · 37 kmHigh 13.8°C · Low 5.8°C · 101 mm rain
- San Francisco in DecemberUnited States · 39 kmHigh 13.5°C · Low 6.3°C · 108 mm rain
- Antioch in DecemberUnited States · 41 kmHigh 13.7°C · Low 6.3°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 Vallejo) is explained once on the Vallejo year overview and on the Sources, method and limits page.