December weather forecastSan Bruno, CA
December
Weather in December
December, the first month of the winter in San Bruno, is still a mild month, with an average temperature fluctuating between 47.7°F (8.7°C) and 55.8°F (13.2°C).Temperature
San Bruno records the coldest temperatures in December, averaging a high of 55.8°F (13.2°C) and a low of 47.7°F (8.7°C).Humidity
In San Bruno, California, the average relative humidity in December is 72%.Rainfall
In San Bruno, in December, during 11 rainfall days, 2.28" (58mm) of precipitation is typically accumulated. Throughout the year, there are 81.8 rainfall days, and 13.46" (342mm) of precipitation is accumulated.Daylight
The month with the shortest days is December, with an average of 9h and 36min of daylight.On the first day of the month, sunrise is at 7:06 am and sunset at 4:51 pm. On the last day of December, sunrise is at 7:24 am and sunset at 5:01 pm PST.
Sunshine
December has the least sunshine of the year, with an average of 5.8h of sunshine.UV index
The months with the lowest UV index are February, November and December, with an average maximum UV index of 3. A UV Index of 3 to 5 symbolizes a medium health hazard from exposure to the Sun's UV rays for the ordinary person.Note: A maximum daily UV index of 3 during December morphs into the following directions:
Undertake precautions - Obligation exists to protect against skin and eye damage. Exposing oneself to the midday Sun can be harmful due to the strong UV radiation; limit your time outside. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
San Bruno, CA
- Average high temperature in December: 55.8°F
The warmest month (with the highest average high temperature) is September (69.8°F).
The month with the lowest average high temperature is December (55.8°F).
- Average low temperature in December: 47.7°F
The month with the highest average low temperature is September (56.5°F).
The coldest month (with the lowest average low temperature) is December (47.7°F).
Average pressure in December
San Bruno, CA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is September (29.92"Hg).
Average wind speed in December
San Bruno, CA
- Average wind speed in December: 7.4mph
The windiest month (with the highest average wind speed) is April (8.5mph).
The calmest months (with the lowest average wind speed) are August and September (6.3mph).
Average humidity in December
San Bruno, CA
- Average humidity in December: 72%
The month with the highest relative humidity is August (79%).
The months with the lowest relative humidity are October and November (71%).
Average rainfall in December
San Bruno, CA
- Average rainfall in December: 2.28"
The wettest month (with the highest rainfall) is February (2.72").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in December
San Bruno, CA
- Average rainfall days in December: 11 days
The month with the highest number of rainy days is March (13.3 days).
The months with the least rainy days are July and August (2.2 days).
Average daylight in December /
Average sunshine in December
San Bruno, CA
- Average daylight in December: 9h and 36min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in December: 5h and 48min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is December (Average sunshine: 5h and 48min).
Average sunshine days in December
San Bruno, CA
- Average sunshine days in December: 19.1 days
The month with the most sunshine days is July (27.3 days).
The month with the least sunshine days is March (16.3 days).
Average UV index in December
San Bruno, CA
- Average UV index in December: 3
The months with the highest UV index are June, July, August and September (UV index 5).
The months with the lowest UV index are February, November and December (UV index 3).
Average cloud cover in December
San Bruno, CA
- Average cloud cover in December: 35
The month with the most cloud cover is March (Cloud cover 37).
The month with the least cloud cover is September (Cloud cover 16).
Average visibility in December
San Bruno, CA
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
