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 May. 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%).
The month of May is characterized by essentially constant daily high temperatures, with daily highs around 69°F throughout the month, exceeding 75°F or dropping below 63°F only one day in ten.
Over the course of May, the length of the day is gradually increasing. The shortest day of the month is May 1 with 13:30 hours of daylight; the longest day is May 30 with 14:09 hours of daylight.
The earliest sunrise is at 5:42am on May 30; the latest sunset is at 7:51pm on May 31; the latest sunrise is at 6:01am on May 1; the earliest sunset is at 7:31pm on May 1.
Daylight savings time is observed in 2012 but it neither starts nor ends in May, so the entire month is in daylight time.
The median cloud cover ranges from 72% (partly cloudy) to 78% (partly cloudy).
On May 16, a representative day, the sky is clear or mostly clear 30% of the time, partly cloudy 15% of the time, and mostly cloudy or overcast 55% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around May 1, occurring in 17% of days. Precipitation is least likely around May 31, occurring in 12% of days.
Throughout May, the most common forms of precipitation are light rain, drizzle, and moderate rain.
Light rain is the most severe precipitation observed during 44% of those days with precipitation. It is most likely around May 1, when it is observed during 9% of all days.
Drizzle is the most severe precipitation observed during 34% of those days with precipitation. It is most likely around May 23, when it is observed during 6% of all days.
Moderate rain is the most severe precipitation observed during 16% of those days with precipitation. It is most likely around May 1, when it is observed during 4% of all days.
Either snow is exceptionally unlikely to fall at this location in May or this station does not reliably report precipitation types.
The relative humidity typically ranges from 56% (mildly humid) to 84% (humid) over the course of a typical May, rarely dropping below 42% (comfortable) and reaching as high as 96% (very humid).
The air is driest around May 1, at which time the relative humidity drops below 64% (mildly humid) three days out of four; it is most humid around May 31, rising above 79% (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 May, the dew point typically varies from 49°F (dry) to 58°F (comfortable) and is rarely below 43°F (dry) or above 62°F (comfortable).
The time of the month between May 1 and May 31 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of May typical wind speeds vary from 1 mph to 13 mph (calm to moderate breeze), rarely exceeding 17 mph (moderate 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 8 mph (gentle breeze) occurs around May 24, at which time the average daily maximum wind speed is 13 mph (moderate breeze).