December weather forecastCastro Valley, CA
December
Weather in December
The first month of the winter, December, is also a moderate month in Castro Valley, California, with an average temperature fluctuating between 43.7°F (6.5°C) and 55.9°F (13.3°C).Temperature
The lowest temperatures are recorded in December, with averages reaching a high of 55.9°F (13.3°C) and a low of 43.7°F (6.5°C).Humidity
The average relative humidity in December in Castro Valley is 70%.Rainfall
In Castro Valley, in December, it is raining for 10.2 days, with typically 1.81" (46mm) of accumulated precipitation. Throughout the year, in Castro Valley, there are 69.2 rainfall days, and 11.1" (282mm) of precipitation is accumulated.Daylight
December has the shortest days of the year in Castro Valley, California, with an average of 9h and 36min of daylight.On the first day of December in Castro Valley, sunrise is at 7:05 am and sunset at 4:49 pm. On the last day of the month, sunrise is at 7:23 am and sunset at 5:00 pm PST.
Sunshine
December has the least sunshine of the year, with an average of 5.9h of sunshine.UV index
January, February, November and December, with an average maximum UV index of 3, are months with the lowest UV index in Castro Valley, California. A UV Index of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for the average person.Note: A typical high UV index of 3 in December suggests the following recommendations:
Preventative actions are necessary - Suggestions to safeguard against sun damage are in order. Around midday, solar radiation is most harmful; hence, exposure should be limited. During bright days, sunglasses that offer UVA and UVB defense are recommended.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Castro Valley, CA
- Average high temperature in December: 55.9°F
The warmest month (with the highest average high temperature) is July (80.2°F).
The month with the lowest average high temperature is December (55.9°F).
- Average low temperature in December: 43.7°F
The month with the highest average low temperature is August (56.5°F).
The coldest months (with the lowest average low temperature) are January and December (43.7°F).
Average pressure in December
Castro Valley, CA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.92"Hg).
Average wind speed in December
Castro Valley, CA
- Average wind speed in December: 5.2mph
The windiest month (with the highest average wind speed) is May (6.6mph).
The calmest month (with the lowest average wind speed) is November (4.6mph).
Average humidity in December
Castro Valley, CA
- Average humidity in December: 70%
The month with the highest relative humidity is March (74%).
The month with the lowest relative humidity is September (61%).
Average rainfall in December
Castro Valley, CA
- Average rainfall in December: 1.81"
The wettest month (with the highest rainfall) is February (2.28").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in December
Castro Valley, CA
- Average rainfall days in December: 10.2 days
The month with the highest number of rainy days is March (12.4 days).
The month with the least rainy days is August (0.9 days).
Average daylight in December /
Average sunshine in December
Castro Valley, 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 6min).
The month with the least sunshine is December (Average sunshine: 5h and 54min).
Average sunshine days in December
Castro Valley, CA
- Average sunshine days in December: 19.4 days
The month with the most sunshine days is August (28.9 days).
The month with the least sunshine days is March (17.3 days).
Average UV index in December
Castro Valley, CA
- Average UV index in December: 3
The month with the highest UV index is June (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in December
Castro Valley, CA
- Average cloud cover in December: 34
The months with the most cloud cover are March and December (Cloud cover 34).
The month with the least cloud cover is July (Cloud cover 7).
Average visibility in December
Castro Valley, 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).
