Average Weather For San Jose, California, USA

Location

This report describes the typical weather at the San Jose International Airport (San Jose, California, United States) weather station over the course of an average year. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.

San Jose, California has a mediterranean climate with dry warm summers and mild winters. The area within 25 mi of this station is covered by grasslands (44%), forests (30%), built-up areas (14%), shrublands (8%), and oceans and seas (3%).

Temperature

Over the course of a year, the temperature typically varies from 42°F to 82°F and is rarely below 35°F or above 91°F.

Daily High and Low Temperature

The daily average low (blue) and high (red) temperature with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

The warm season lasts from June 6 to October 11 with an average daily high temperature above 77°F. The hottest day of the year is September 1, with an average high of 82°F and low of 60°F.

The cold season lasts from November 27 to February 22 with an average daily high temperature below 63°F. The coldest day of the year is December 25, with an average low of 42°F and high of 58°F.

Fraction of Time Spent in Various Temperature Bands

The average fraction of time spent in various temperature bands: frigid (below 15°F), freezing (15°F to 32°F), cold (32°F to 50°F), cool (50°F to 65°F), comfortable (65°F to 75°F), warm (75°F to 85°F), hot (85°F to 100°F) and sweltering (above 100°F).

Sun

The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:35 hours of daylight; the longest day is June 20 with 14:45 hours of daylight.

Daily Hours of Daylight and Twilight

The number of hours during which the Sun is visible (black line), with various degrees of daylight, twilight, and night, indicated by the color bands. From bottom (most yellow) to top (most gray): full daylight, solar twilight (Sun is visible but less than 6° from the horizon), civil twilight (Sun is not visible but is less than 6° below the horizon), nautical twilight (Sun is between 6° and 12° below the horizon), astronomical twilight (Sun is between 12° and 18° below the horizon), and full night.

The earliest sunrise is at 5:46am on June 12 and the latest sunset is at 8:33pm on June 29. The latest sunrise is at 7:35am on November 3 and the earliest sunset is at 4:49pm on December 7.

Daylight savings time (DST) is observed in this location during 2012, starting in the spring on March 11 and ending in the fall on November 4.

Daily Sunrise & Sunset with Twilight and Daylight Savings Time

The solar day over the course of the year 2012 . From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (solar, civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight savings time are indicated by the "DST" labels.

Clouds

The median cloud cover ranges from 21% (mostly clear) to 78% (partly cloudy). The sky is cloudiest on January 25 and clearest on July 12. The clearer part of the year begins around May 1. The cloudier part of the year begins around November 4.

Median Cloud Cover

The median daily cloud cover (black line) with percentile bands (inner band from 40th to 60th percentile, outer band from 25th to 75th percentile).

On July 12, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 71% of the time, and overcast or mostly cloudy 20% of the time.

On January 25, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 66% of the time, and clear or mostly clear 25% of the time.

Cloud Cover Types

The fraction of time spent in each of the five sky cover categories. From top (most blue) to bottom (most gray), the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data.

Precipitation

The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around February 4, occurring in 34% of days. Precipitation is least likely around July 11, occurring in 1% of days.

Probability of Precipitation at Some Point in the Day

The fraction of days in which various types of precipitation are observed. If more than one type of precipitation is reported in a given day, the more severe precipitation is counted. For example, if light rain is observed in the same day as a thunderstorm, that day counts towards the thunderstorm totals. The order of severity is from the top down in this graph, with the most severe at the bottom.

Over the entire year, the most common forms of precipitation are light rain and moderate rain.

Light rain is the most severe precipitation observed during 45% of those days with precipitation. It is most likely around February 24, when it is observed during 15% of all days.

Moderate rain is the most severe precipitation observed during 42% of those days with precipitation. It is most likely around January 20, when it is observed during 16% of all days.

Types of Precipitation Throughout the Year

Relative frequency of various types of precipitation over the course of a typical year.

During the warm season, which lasts from June 6 to October 11, there is a 4% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light rain (51% of days with precipitation have at worst light rain), moderate rain (25%), and thunderstorms (14%).

During the cold season, which lasts from November 27 to February 22, there is a 31% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of moderate rain (47% of days with precipitation have at worst moderate rain), light rain (41%), and heavy rain (8%).

Warm Season Precipitation

Cold Season Precipitation

Relative frequency of various types of precipitation during the warm and cold seasons respectively.

Snow

Either snow is exceptionally unlikely to fall at any time during the year at this location or this station does not reliably report precipitation types.

Humidity

The relative humidity typically ranges from 38% (comfortable) to 96% (very humid) over the course of the year, rarely dropping below 20% (dry) and reaching as high as 100% (very humid).

The air is driest around October 3, at which time the relative humidity drops below 48% (comfortable) three days out of four; it is most humid around January 4, exceeding 93% (very humid) three days out of four.

Relative Humidity

The average daily high (blue) and low (brown) relative humidity with percentile bands (inner bands from 25th to 75th percentile, outer bands from 10th to 90th percentile).

Dew Point

Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.

Over the course of a year, the dew point typically varies from 35°F (dry) to 59°F (comfortable) and is rarely below 25°F (dry) or above 63°F (mildy humid).

The time of the year between April 15 and November 14 is the most comfortable, with dew points that are neither too dry nor too muggy.

Dew Point

The daily average low (blue) and high (red) dew point with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Wind

Over the course of the year typical wind speeds vary from 0 mph to 18 mph (calm to moderate breeze), rarely exceeding 22 mph (fresh breeze).

The highest average wind speed of 8 mph (gentle breeze) occurs around May 31, at which time the average daily maximum wind speed is 18 mph (moderate breeze).

The lowest average wind speed of 5 mph (light breeze) occurs around November 10, at which time the average daily maximum wind speed is 12 mph (gentle breeze).

Wind Speed

The average daily minimum (red), maximum (green), and average (black) wind speed with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
The wind is most often out of the north west (24% of the time) and north (16% of the time). The wind is least often out of the north east (1% of the time), east (1% of the time), and south west (2% of the time).

Wind Directions Over the Entire Year

The fraction of time spent with the wind blowing from the various directions over the entire year. Values do not sum to 100% because the wind direction is undefined when the wind speed is zero.

Fraction of Time Spent with Various Wind Directions

The fraction of time spent with the wind blowing from the various directions on a daily basis. Stacked values do not always sum to 100% because the wind direction is undefined when the wind speed is zero.