This report describes the typical weather at the San Luis Obispo County Regional Airport (San Luis Obispo, California, United States) weather station over the course of an average year. It is based on the historical records from 1984 to 2012. Earlier records are either unavailable or unreliable.
San Luis Obispo, California has a mediterranean climate with dry warm summers and mild winters. The area within 25 mi of this station is covered by grasslands (58%), oceans and seas (29%), forests (8%), and shrublands (4%).
Over the course of a year, the temperature typically varies from 40°F to 79°F and is rarely below 33°F or above 90°F.
The warm season lasts from June 25 to October 18 with an average daily high temperature above 76°F. The hottest day of the year is September 1, with an average high of 79°F and low of 55°F.
The cold season lasts from December 1 to March 13 with an average daily high temperature below 67°F. The coldest day of the year is December 22, with an average low of 40°F and high of 64°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:47 hours of daylight; the longest day is June 20 with 14:32 hours of daylight.
The earliest sunrise is at 5:47am on June 14 and the latest sunset is at 8:22pm on June 26. The latest sunrise is at 7:27am on November 3 and the earliest sunset is at 4:50pm on December 7.
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 11% (mostly clear) to 42% (partly cloudy). The sky is cloudiest on August 18 and clearest on November 24. The clearer part of the year begins around September 30. The cloudier part of the year begins around January 20.
On November 24, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 62% of the time, and overcast or mostly cloudy 28% of the time.
On August 18, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 36% of the time, and clear or mostly clear 52% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around February 15, occurring in 33% of days. Precipitation is least likely around August 20, occurring in 5% 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 39% of those days with precipitation. It is most likely around February 20, when it is observed during 12% of all days.
Moderate rain is the most severe precipitation observed during 33% of those days with precipitation. It is most likely around February 5, when it is observed during 14% of all days.
Drizzle is the most severe precipitation observed during 13% of those days with precipitation. It is most likely around July 1, when it is observed during 4% of all days.
During the warm season, which lasts from June 25 to October 18, 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 drizzle (42% of days with precipitation have at worst drizzle), light rain (33%), moderate rain (13%), and thunderstorms (10%).
During the cold season, which lasts from December 1 to March 13, there is a 29% 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 moderate rain (41% of days with precipitation have at worst moderate rain), light rain (38%), and heavy rain (12%).
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 40% (comfortable) to 96% (very humid) over the course of the year, rarely dropping below 17% (dry) and reaching as high as 100% (very humid).
The air is driest around November 23, at which time the relative humidity drops below 52% (mildly humid) three days out of four; it is most humid around February 27, exceeding 93% (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 year, the dew point typically varies from 34°F (dry) to 57°F (comfortable) and is rarely below 22°F (dry) or above 60°F (comfortable).
The time of the year between February 28 and November 16 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 20 mph (calm to fresh breeze), rarely exceeding 27 mph (strong breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around May 29, at which time the average daily maximum wind speed is 20 mph (fresh breeze).
The lowest average wind speed of 4 mph (light breeze) occurs around December 18, at which time the average daily maximum wind speed is 13 mph (moderate breeze).