December weather forecastAltadena, CA
December
Weather in December
December, the first month of the winter in Altadena, is still a comfortable month, with an average temperature ranging between min 45.5°F (7.5°C) and max 61°F (16.1°C).Temperature
Altadena witnesses the coldest weather in December, with temperatures averaging a high of 61°F (16.1°C) and a low of 45.5°F (7.5°C).Humidity
The average relative humidity in December is 52%.Rainfall
In December, the rain falls for 6.2 days. Throughout December, 1.77" (45mm) of precipitation is accumulated. In Altadena, during the entire year, the rain falls for 52 days and collects up to 8.82" (224mm) of precipitation.Daylight
With an average of 9h and 54min of daylight, December has the shortest days of the year.On the first day of the month, sunrise is at 6:40 am and sunset at 4:42 pm. On the last day of December, sunrise is at 6:58 am and sunset at 4:53 pm PST.
Sunshine
The months with the least sunshine are February and December, with an average of 6.9h of sunshine.UV index
With an average maximum UV index of 3, December is the month with the lowest UV index. A UV Index value of 3 to 5 symbolizes a medium health hazard from exposure to the Sun's UV radiation for the average person.Note: A typical high UV index of 3 in December suggests the following recommendations:
Put precautions into practice - Protective measures against sun-induced damage are advised. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Altadena, CA
- Average high temperature in December: 61°F
The warmest month (with the highest average high temperature) is August (86.2°F).
The month with the lowest average high temperature is December (61°F).
- Average low temperature in December: 45.5°F
The month with the highest average low temperature is August (64.4°F).
The coldest month (with the lowest average low temperature) is December (45.5°F).
Average pressure in December
Altadena, CA
- Average pressure in December: 30.08"Hg
The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).
Average wind speed in December
Altadena, CA
- Average wind speed in December: 5.5mph
The windiest month (with the highest average wind speed) is April (5.8mph).
The calmest month (with the lowest average wind speed) is September (4.4mph).
Average humidity in December
Altadena, CA
- Average humidity in December: 52%
The months with the highest relative humidity are March, May and June (56%).
The month with the lowest relative humidity is November (46%).
Average rainfall in December
Altadena, CA
- Average rainfall in December: 1.77"
The wettest month (with the highest rainfall) is February (1.81").
The driest month (with the least rainfall) is June (0.04").
Average rainfall days in December
Altadena, CA
- Average rainfall days in December: 6.2 days
The month with the highest number of rainy days is March (7.5 days).
The month with the least rainy days is June (1.3 days).
Average daylight in December /
Average sunshine in December
Altadena, CA
- Average daylight in December: 9h and 54min
The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 9h and 54min).
- Average sunshine in December: 6h and 54min
The months with the most sunshine are June and July (Average sunshine: 12h and 6min).
The months with the least sunshine are February and December (Average sunshine: 6h and 54min).
Average sunshine days in December
Altadena, CA
- Average sunshine days in December: 23.5 days
The month with the most sunshine days is June (27.2 days).
The month with the least sunshine days is February (21.3 days).
Average UV index in December
Altadena, CA
- Average UV index in December: 3
The months with the highest UV index are June, July, August and September (UV index 6).
The month with the lowest UV index is December (UV index 3).
Average cloud cover in December
Altadena, CA
- Average cloud cover in December: 21
The month with the most cloud cover is March (Cloud cover 22).
The month with the least cloud cover is August (Cloud cover 5).
Average visibility in December
Altadena, 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).
