This report describes the typical weather at the San Francisco International Airport (San Francisco, California, United States) weather station over the course of an average February. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
San Francisco, California has a mediterranean climate with dry warm summers and mild winters. The area within 25 mi of this station is covered by oceans and seas (48%), built-up areas (16%), grasslands (14%), forests (13%), and shrublands (8%).
The month of February is characterized by gradually rising daily high temperatures, with daily highs around 58°F throughout the month, exceeding 66°F or dropping below 52°F only one day in ten.
Over the course of February, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 1:02 hours, implying an average day-over-day increase of 2.2 minutes.
The shortest day of the month is February 1 with 10:19 hours of daylight; the longest day is February 29 with 11:21 hours of daylight.
The earliest sunrise is at 6:42am on February 29; the latest sunset is at 6:03pm on February 29; the latest sunrise is at 7:14am on February 1; the earliest sunset is at 5:33pm on February 1.
Daylight savings time is observed in 2012 but it neither starts nor ends in February, so the entire month is in standard time.
The median cloud cover is 67% (partly cloudy) and does not vary substantially over the course of the month.
On February 15, a representative day, the sky is clear or mostly clear 33% of the time, partly cloudy 22% of the time, and mostly cloudy or overcast 45% of the time.
The average probability that some form of precipitation will be observed in a given day is 42%, with little variation over the course of the month.
Throughout February, the most common forms of precipitation are moderate rain, light rain, and heavy rain.
Moderate rain is the most severe precipitation observed during 40% of those days with precipitation. It is most likely around February 4, when it is observed during 17% of all days.
Light rain is the most severe precipitation observed during 39% of those days with precipitation. It is most likely around February 24, when it is observed during 17% of all days.
Heavy rain is the most severe precipitation observed during 10% of those days with precipitation. It is most likely around February 1, when it is observed during 5% of all days.
Either snow is exceptionally unlikely to fall at this location in February or this station does not reliably report precipitation types.
The relative humidity typically ranges from 58% (mildly humid) to 93% (very humid) over the course of a typical February, rarely dropping below 37% (comfortable) and reaching as high as 100% (very humid).
The air is driest around February 29, at which time the relative humidity drops below 68% (mildly humid) three days out of four; it is most humid around February 1, rising above 89% (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 February, the dew point typically varies from 39°F (dry) to 49°F (dry) and is rarely below 30°F (dry) or above 55°F (very comfortable).
Over the course of February typical wind speeds vary from 0 mph to 18 mph (calm to fresh breeze), rarely exceeding 27 mph (strong breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around February 24, at which time the average daily maximum wind speed is 18 mph (fresh breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around February 1, at which time the average daily maximum wind speed is 15 mph (moderate breeze).