December weather forecastFoster City, CA
December
Weather in December
December, the first month of the winter in Foster City, is still a mild month, with temperature in the range of an average low of 47.5°F (8.6°C) and an average high of 55.8°F (13.2°C).Temperature
In Foster City, the month of December registers the lowest temperatures, averaging 55.8°F (13.2°C) at the peak and 47.5°F (8.6°C) at the lowest.Humidity
In Foster City, the average relative humidity in December is 72%.Rainfall
In December, the rain falls for 5.5 days. Throughout December, 0.35" (9mm) of precipitation is accumulated. In Foster City, during the entire year, the rain falls for 32.6 days and collects up to 2.13" (54mm) of precipitation.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 7:05 am and sunset at 4:51 pm. On the last day of December, sunrise is at 7:23 am and sunset at 5:01 pm PST.
Sunshine
The month with the least sunshine is December, with an average of 5.9h of sunshine.UV index
February and December, with an average maximum UV index of 3, are months with the lowest UV index. A UV Index estimate of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for the ordinary person.Note: In December, the maximum UV index of 3 suggests these recommendations:
Preventative actions are necessary - Suggestions to safeguard against sun damage are in order. To guard against the harmful effects of the Sun, minimize exposure during midday. Your best bet for sun defense on the face, eyes, and neck is a hat with a wide brim.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Foster City, CA
- Average high temperature in December: 55.8°F
The warmest months (with the highest average high temperature) are August and September (71.2°F).
The month with the lowest average high temperature is December (55.8°F).
- Average low temperature in December: 47.5°F
The month with the highest average low temperature is September (56.7°F).
The coldest month (with the lowest average low temperature) is January (46.9°F).
Average pressure in December
Foster City, 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
Foster City, CA
- Average wind speed in December: 6.9mph
The windiest month (with the highest average wind speed) is April (8mph).
The calmest months (with the lowest average wind speed) are August, September and October (5.9mph).
Average humidity in December
Foster City, CA
- Average humidity in December: 72%
The months with the highest relative humidity are March and August (76%).
The months with the lowest relative humidity are October and November (70%).
Average rainfall in December
Foster City, CA
- Average rainfall in December: 0.35"
The wettest month (with the highest rainfall) is February (0.55").
The driest months (with the least rainfall) are June, July and August (0").
Average rainfall days in December
Foster City, CA
- Average rainfall days in December: 5.5 days
The month with the highest number of rainy days is March (6.8 days).
The month with the least rainy days is July (0.3 days).
Average daylight in December /
Average sunshine in December
Foster City, 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 54min
The month with the most sunshine is July (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 5h and 54min).
Average sunshine days in December
Foster City, CA
- Average sunshine days in December: 24.4 days
The month with the most sunshine days is July (30.4 days).
The month with the least sunshine days is February (23.3 days).
Average UV index in December
Foster City, 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 and December (UV index 3).
Average cloud cover in December
Foster City, CA
- Average cloud cover in December: 34
The month with the most cloud cover is March (Cloud cover 35).
The month with the least cloud cover is July (Cloud cover 11).
Average visibility in December
Foster City, 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).
