December weather forecastAtherton, CA
December
Weather in December
December, the first month of the winter in Atherton, is still a mild month, with an average temperature varying between 55.9°F (13.3°C) and 46.6°F (8.1°C).Temperature
With average high temperatures of 55.9°F (13.3°C) and lows of 46.6°F (8.1°C), December is the coldest month.Humidity
The average relative humidity in December is 72%.Rainfall
In Atherton, in December, during 10.2 rainfall days, 2.05" (52mm) of precipitation is typically accumulated. Throughout the year, there are 73.4 rainfall days, and 11.89" (302mm) of precipitation is accumulated.Daylight
December has the shortest days of the year, with an average of 9h and 36min of daylight.On the first day of December, sunrise is at 7:05 am and sunset at 4:50 pm. On the last day of the month, sunrise is at 7:23 am and sunset at 5:01 pm PST.
Sunshine
With an average of 5.8h of sunshine, December has the least sunshine of the year.UV index
The months with the lowest UV index are November and December, with an average maximum UV index of 3. A UV Index estimate of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV radiation for average individuals.Note: The daily maximum UV index of 3 in December interprets into the following advice:
Ensure safety - Imperative it is to shield skin and eyes from damage. Limiting sun exposure during midday hours helps in reducing the harmful effects of UV radiation. A wide-brimmed hat is a staple for defending the face, eyes, ears, and neck from the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Atherton, CA
- Average high temperature in December: 55.9°F
The warmest months (with the highest average high temperature) are July and August (73°F).
The month with the lowest average high temperature is December (55.9°F).
- Average low temperature in December: 46.6°F
The month with the highest average low temperature is September (56.7°F).
The coldest month (with the lowest average low temperature) is February (46°F).
Average pressure in December
Atherton, 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
Atherton, CA
- Average wind speed in December: 6.5mph
The windiest month (with the highest average wind speed) is April (7.5mph).
The calmest months (with the lowest average wind speed) are August, September and October (5.5mph).
Average humidity in December
Atherton, CA
- Average humidity in December: 72%
The month with the highest relative humidity is March (75%).
The month with the lowest relative humidity is October (68%).
Average rainfall in December
Atherton, CA
- Average rainfall in December: 2.05"
The wettest month (with the highest rainfall) is February (2.36").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in December
Atherton, CA
- Average rainfall days in December: 10.2 days
The month with the highest number of rainy days is March (12.8 days).
The month with the least rainy days is August (0.8 days).
Average daylight in December /
Average sunshine in December
Atherton, 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: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 5h and 48min).
Average sunshine days in December
Atherton, CA
- Average sunshine days in December: 19.3 days
The month with the most sunshine days is August (27.6 days).
The month with the least sunshine days is March (17.5 days).
Average UV index in December
Atherton, 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 November and December (UV index 3).
Average cloud cover in December
Atherton, 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 9).
Average visibility in December
Atherton, 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).
