This report describes the typical weather at the Livermore Municipal Airport (Livermore, California, United States) weather station over the course of an average year. It is based on the historical records from 1998 to 2012. Earlier records are either unavailable or unreliable.
Livermore, California has a mediterranean climate with dry warm summers and mild winters. The area within 25 mi of this station is covered by grasslands (62%), built-up areas (12%), shrublands (10%), croplands (6%), and oceans and seas (4%).
Over the course of a year, the temperature typically varies from 38°F to 87°F and is rarely below 30°F or above 98°F.
The warm season lasts from June 16 to September 25 with an average daily high temperature above 81°F. The hottest day of the year is September 1, with an average high of 87°F and low of 57°F.
The cold season lasts from November 19 to March 8 with an average daily high temperature below 62°F. The coldest day of the year is January 2, with an average low of 38°F and high of 56°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:34 hours of daylight; the longest day is June 20 with 14:46 hours of daylight.
The earliest sunrise is at 5:44am on June 13 and the latest sunset is at 8:34pm on June 27. The latest sunrise is at 7:36am on November 3 and the earliest sunset is at 4:48pm 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 3% (clear) to 39% (mostly clear). The sky is cloudiest on January 28 and clearest on June 29. The clearer part of the year begins around March 24. The cloudier part of the year begins around December 13.
On June 29, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 84% of the time, and overcast or mostly cloudy 16% of the time.
On January 28, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 46% of the time, and clear or mostly clear 50% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around February 6, occurring in 40% of days. Precipitation is least likely around July 29, occurring in 2% of days.
Over the entire year, the most common forms of precipitation are light rain, moderate rain, and heavy rain.
Light rain is the most severe precipitation observed during 52% of those days with precipitation. It is most likely around February 22, when it is observed during 19% of all days.
Moderate rain is the most severe precipitation observed during 32% of those days with precipitation. It is most likely around February 14, when it is observed during 16% of all days.
Heavy rain is the most severe precipitation observed during 11% of those days with precipitation. It is most likely around December 28, when it is observed during 6% of all days.
During the warm season, which lasts from June 16 to September 25, there is a 3% 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 (47% of days with precipitation have at worst light rain), thunderstorms (29%), moderate rain (18%), and heavy rain (6%).
During the cold season, which lasts from November 19 to March 8, there is a 35% 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 (50% of days with precipitation have at worst light rain), moderate rain (33%), and heavy rain (13%).
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 28% (dry) to 93% (very humid) over the course of the year, rarely dropping below 16% (dry) and reaching as high as 100% (very humid).
The air is driest around September 1, at which time the relative humidity drops below 36% (comfortable) three days out of four; it is most humid around January 4, exceeding 91% (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 33°F (dry) to 56°F (comfortable) and is rarely below 22°F (dry) or above 60°F (comfortable).
The time of the year between May 17 and October 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 17 mph (calm to moderate breeze), rarely exceeding 21 mph (fresh breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around July 20, at which time the average daily maximum wind speed is 17 mph (moderate breeze).
The lowest average wind speed of 4 mph (light breeze) occurs around November 9, at which time the average daily maximum wind speed is 12 mph (gentle breeze).