December weather forecast and climate
Altadena, CA

Weather in December

The first month of the winter, December, is also an enjoyable month in Altadena, California, with average temperature ranging between max 61°F (16.1°C) and min 45.5°F (7.5°C).

Temperature

With an average high-temperature of 61°F (16.1°C) and an average low-temperature of 45.5°F (7.5°C), December is the coldest month.

Humidity

In Altadena, the average relative humidity is 52%.

Rainfall

In December, the rain falls for 6.2 days. Throughout December, 1.77" (45mm) of precipitation is accumulated. Throughout the year, there are 52 rainfall days, and 8.82" (224mm) of precipitation is accumulated.

Daylight

With an average of 9.9h of daylight, December has the shortest days of the year.

Sunshine

Months with the least sunshine in Altadena 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 unprotected exposure to the Sun's UV rays for the ordinary person.
Note: In December, the average maximum UV index of 3 translate into the following recommendations:
Take precautions - Protection against the skin and eye damage is obliged. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.
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FAQ

What is the coldest month in Altadena?

December is the coldest month in Altadena, with an average high-temperature of 61°F (16.1°C) and an average low-temperature of 45.5°F (7.5°C).

What is the temperature in December in Altadena?

In Altadena, California, in December, the average high-temperature is 61°F (16.1°C), and the average low-temperature is 45.5°F (7.5°C).

What is the average humidity in December in Altadena?

In December, the average relative humidity in Altadena, California, is 52%.

How much does it rain in Altadena in December?

In Altadena, in December, it is raining for 6.2 days, with typically 1.77" (45mm) of accumulated precipitation.

What is the month with the shortest days in Altadena?

With an average of 9.9h of daylight, December has the shortest days of the year in Altadena.

How many hours of daylight does Altadena have in December?

In December, the average length of the day in Altadena, California, is 9.9h.

What is the month with the least sunshine in Altadena?

Months with the least sunshine are February and December, with an average of 6.9h of sunshine.

How many hours of sunshine does Altadena have in December?

The average sunshine in December in Altadena, California, is 6.9h.

What is the month with the lowest UV index in Altadena?

The month with the lowest UV index in Altadena, California, is December, with an average maximum UV index of 3.

What is the UV index intensity in December in Altadena?

In December, the average daily maximum UV index in Altadena is 3. A UV Index value of 3 to 5 symbolizes a medium health risk from the exposure to the Sun's UV rays.

Average temperature in December
Altadena, CA

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).

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Average pressure in December
Altadena, CA

Average pressure in December - Altadena, CA
  • Average pressure in December: 30.08"

The month with the highest atmospheric pressure is January (30.11").
The month with the lowest atmospheric pressure is June (29.88").

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Average wind speed in December
Altadena, CA

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).

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Average humidity in December
Altadena, CA

Average humidity in December - Altadena, CA
  • Average humidity in December: 52%

Months with the highest relative humidity are March, May and June (56%).
The month with the lowest relative humidity is November (46%).

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Average rainfall in December
Altadena, CA

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").

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Average rainfall days in December
Altadena, CA

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).

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Average daylight in December /
Average sunshine in December
Altadena, CA

Average daylight in December / Average sunshine in December - Altadena, CA
  • Average daylight in December: 9.9h

The month with the longest days is June (Average daylight: 14.4h).
The month with the shortest days is December (Average daylight: 9.9h).

  • Average sunshine in December: 6.9h

Months with the most sunshine are June and July (Average sunshine: 12.1h).
Months with the least sunshine are February and December (Average sunshine: 6.9).

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Average sunshine days in December
Altadena, CA

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).

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Average UV index in December
Altadena, CA

Average UV index in December - Altadena, CA
  • Average UV index in December: 3

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).

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Average cloud cover in December
Altadena, CA

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).

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Average visibility in December
Altadena, CA

Average visibility in December - Altadena, CA
  • Average visibility in December: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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