This report describes the typical weather at the Oakland International Airport (Oakland, 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.
Oakland, California has a mediterranean climate with dry warm summers and mild winters. The area within 25 mi of this station is covered by grasslands (31%), oceans and seas (28%), built-up areas (19%), shrublands (10%), and forests (9%).
The month of April is characterized by gradually rising daily high temperatures, with daily highs around 64°F throughout the month, exceeding 74°F or dropping below 57°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 1:06 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 13:45 hours of daylight.
The earliest sunrise is at 6:14am on April 30; the latest sunset is at 7:59pm on April 30; the latest sunrise is at 6:53am on April 1; the earliest sunset is at 7:32pm 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 55% (partly cloudy) to 64% (partly cloudy). The trend is for the sky to be clearing with the median cloud cover decreasing by 7% from the start to the end of the month.
On April 15, a representative day, the sky is clear or mostly clear 37% of the time, partly cloudy 20% of the time, and mostly cloudy or overcast 44% 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 29% of days. Precipitation is least likely around April 30, occurring in 18% 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 45% of those days with precipitation. It is most likely around April 1, when it is observed during 12% of all days.
Moderate rain is the most severe precipitation observed during 40% of those days with precipitation. It is most likely around April 1, when it is observed during 12% 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 54% (mildly humid) to 92% (very humid) over the course of a typical April, rarely dropping below 36% (comfortable) and reaching as high as 100% (very humid).
The air is driest around April 5, at which time the relative humidity drops below 64% (mildly humid) three days out of four; it is most humid around April 26, rising above 87% (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 42°F (dry) to 53°F (very comfortable) and is rarely below 34°F (dry) or above 58°F (comfortable).
The time of the month between April 1 and April 30 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of April typical wind speeds vary from 0 mph to 17 mph (calm to moderate breeze), rarely exceeding 24 mph (fresh breeze).
The highest average wind speed of 10 mph (gentle 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 10 mph (gentle breeze) occurs around April 3, at which time the average daily maximum wind speed is 17 mph (moderate breeze).