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%).
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.
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.
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.
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.
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.
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.
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.
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.
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%).
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.
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.
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.
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).