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 April. 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%).
The month of April is characterized by rising daily high temperatures, with daily highs increasing from 67°F to 72°F over the course of the month, exceeding 82°F or dropping below 59°F only one day in ten.
Over the course of April, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 1:05 hours, implying an average day-over-day increase of 2.2 minutes.
The shortest day of the month is April 1 with 12:39 hours of daylight; the longest day is April 30 with 13:44 hours of daylight.
The earliest sunrise is at 6:13am on April 30; the latest sunset is at 7:57pm on April 30; the latest sunrise is at 6:52am on April 1; the earliest sunset is at 7:31pm on April 1.
Daylight savings time is observed in 2012 but it neither starts nor ends in April, so the entire month is in daylight time.
The median cloud cover ranges from 50% (partly cloudy) to 63% (partly cloudy). The trend is for the sky to be clearing with the median cloud cover decreasing by 13% from the start to the end of the month.
On April 30, the clearest day of the month, the sky is clear, mostly clear, or partly cloudy 56% of the time, and overcast or mostly cloudy 36% of the time.
On April 1, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 61% of the time, and clear or mostly clear 30% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around April 1, occurring in 25% of days. Precipitation is least likely around April 30, occurring in 15% of days.
Throughout April, the most common forms of precipitation are light rain and moderate rain.
Light rain is the most severe precipitation observed during 53% of those days with precipitation. It is most likely around April 1, when it is observed during 13% of all days.
Moderate rain is the most severe precipitation observed during 35% of those days with precipitation. It is most likely around April 1, when it is observed during 10% of all days.
Either snow is exceptionally unlikely to fall at this location in April or this station does not reliably report precipitation types.
The relative humidity typically ranges from 41% (comfortable) to 93% (very humid) over the course of a typical April, rarely dropping below 25% (dry) and reaching as high as 100% (very humid).
The air is driest around April 29, at which time the relative humidity drops below 49% (comfortable) three days out of four; it is most humid around April 1, rising above 88% (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 typical April, the dew point typically varies from 39°F (dry) to 51°F (very comfortable) and is rarely below 31°F (dry) or above 57°F (comfortable).
Over the course of April typical wind speeds vary from 0 mph to 17 mph (calm to moderate breeze), rarely exceeding 22 mph (fresh breeze).
The highest average wind speed of 8 mph (light breeze) occurs around April 30, at which time the average daily maximum wind speed is 17 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around April 1, at which time the average daily maximum wind speed is 16 mph (moderate breeze).