Altadena, California 

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Climate in Altadena, California

Altadena, California gets 23 inches of rain, on average, per year. The US average is 38 inches of rain per year.

Altadena averages 0 inches of snow per year. The US average is 28 inches of snow per year.

On average, there are 287 sunny days per year in Altadena. The US average is 205 sunny days.

Altadena gets some kind of precipitation, on average, 37 days per year. Precipitation is rain, snow, sleet, or hail that falls to the ground. In order for precipitation to be counted you have to get at least .01 inches on the ground to measure.

Weather Highlights

Summer High: the July high is around 86 degrees
Winter Low: the January low is 47
Rain: averages 23 inches of rain a year
Snow: averages 0 inches of snow a year


The annual BestPlaces Comfort Index for Altadena is 9.1 (10=best), which means it is one of the most pleasant places in California.

9.4 / 8.7

Summer   /   Winter
June, October and May are the most pleasant months in Altadena, while January and February are the least comfortable months.

Climate Averages
  Altadena, CaliforniaUnited States
  22.5 in.38.1 in.
  0.0 in.27.8 in.
  37.4 days106.2 days
  287 days205 days
  1358 ft.2443 ft.


Many people confuse weather and climate but they are different. Weather is the conditions of the atmosphere over a short period of time, and climate is how the atmosphere is over long periods of time.

Weather is how the atmosphere is behaving and its effects upon life and human activities. Weather can change from minute-to-minute. Most people think of weather in terms of temperature, humidity, precipitation, cloudiness, brightness, visibility, wind, and atmospheric pressure.

Climate is the description of the long-term pattern of weather in a place. Climate can mean the average weather for a particular region and time period taken over 30 years. Climate is the average of weather over time.

August is the hottest month for Altadena with an average high temperature of 88.1°, which ranks it as about average compared to other places in California. In Altadena, there are 6 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Altadena are May, October and June.

In Altadena, there are 44.2 days annually when the high temperature is over 90°, which is about average compared to other places in California.

December has the coldest nighttime temperatures for Altadena with an average of 45.9°. This is one of the warmest places in California.

In Altadena, there are 0.8 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in California.

In Altadena, there are 0.0 days annually when the nighttime low temperature falls below zero°, which is about average compared to other places in California.

Humidity in Altadena is generally quite low and comfortable. There are few days during the summer when the humidity becomes unpleasant. The most humid months (but still comfortable) are July, August and June.

February is the wettest month in Altadena with 5.5 inches of rain, and the driest month is July with 0.1 inches. The wettest season is Spring with 59% of yearly precipitation and 2% occurs in Autumn, which is the driest season. The annual rainfall of 22.5 inches in Altadena means that it is wetter than most places in California.

February is the rainiest month in Altadena with 6.4 days of rain, and July is the driest month with only 0.4 rainy days. There are 37.4 rainy days annually in Altadena, which is less rainy than most places in California. The rainiest season is Spring when it rains 46% of the time and the driest is Autumn with only a 5% chance of a rainy day.

There is rarely any recorded snowfall in Altadena, ranking it as one of the least snowy places in California. Any measurable snowfall is a rare occurance in Altadena.

  • Annual Rainfall (US Avg: 36.5")
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    Reviews for Altadena    1 Reviews
    Altadena: High and Dry in L.A. - 8/13/2010
    I live just above the 1500 foot elevation at the edge of the San Gabriel Mountains in the L.A. suburb of Altadena--just above Pasadena. We're above the low morning fog... Read More

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