This report describes the typical weather at the San Diego International Airport (San Diego, 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 Diego, California has a cold semi-arid steppe climate. The area within 25 mi of this station is covered by oceans and seas (46%), shrublands (39%), and built-up areas (12%).
Over the course of a year, the temperature typically varies from 49°F to 77°F and is rarely below 44°F or above 83°F.
The warm season lasts from July 9 to October 4 with an average daily high temperature above 74°F. The hottest day of the year is August 29, with an average high of 77°F and low of 67°F.
The cold season lasts from November 30 to April 9 with an average daily high temperature below 67°F. The coldest day of the year is December 23, with an average low of 49°F and high of 65°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:59 hours of daylight; the longest day is June 20 with 14:18 hours of daylight.
The earliest sunrise is at 5:40am on June 12 and the latest sunset is at 8:01pm on June 28. The latest sunrise is at 7:09am on November 3 and the earliest sunset is at 4:42pm on December 5.
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 42% (partly cloudy) to 78% (partly cloudy). The sky is cloudiest on May 25 and clearest on November 27. The clearer part of the year begins around October 14. The cloudier part of the year begins around February 3.
On November 27, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 65% of the time, and overcast or mostly cloudy 35% of the time.
On May 25, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 71% of the time, and clear or mostly clear 29% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around February 27, occurring in 29% of days. Precipitation is least likely around August 5, occurring in 6% of days.
Over the entire year, the most common forms of precipitation are light rain, moderate rain, and drizzle.
Light rain is the most severe precipitation observed during 45% of those days with precipitation. It is most likely around February 13, when it is observed during 14% of all days.
Moderate rain is the most severe precipitation observed during 30% of those days with precipitation. It is most likely around February 1, when it is observed during 11% of all days.
Drizzle is the most severe precipitation observed during 13% of those days with precipitation. It is most likely around May 23, when it is observed during 6% of all days.
During the warm season, which lasts from July 9 to October 4, there is a 7% 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 (41% of days with precipitation have at worst light rain), drizzle (26%), moderate rain (17%), and thunderstorms (14%).
During the cold season, which lasts from November 30 to April 9, there is a 25% 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 (46% of days with precipitation have at worst light rain), moderate rain (37%), and heavy rain (9%).
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 42% (comfortable) to 88% (very humid) over the course of the year, rarely dropping below 15% (dry) and reaching as high as 100% (very humid).
The air is driest around December 6, at which time the relative humidity drops below 58% (mildly humid) three days out of four; it is most humid around August 30, exceeding 83% (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 65°F (mildy humid) and is rarely below 19°F (dry) or above 69°F (muggy).
The time of the year between January 1 and December 31 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 14 mph (calm to moderate breeze), rarely exceeding 19 mph (fresh breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around May 3, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 5 mph (light breeze) occurs around December 24, at which time the average daily maximum wind speed is 11 mph (gentle breeze).