This report describes the typical weather at the Fresno Yosemite International Airport (Fresno, California, United States) weather station over the course of an average December. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Fresno, California has a cold semi-arid steppe climate. The area within 25 mi of this station is covered by grasslands (57%), croplands (28%), forests (11%), and built-up areas (2%).
The month of December is characterized by falling daily high temperatures, with daily highs decreasing from 59°F to 53°F over the course of the month, exceeding 66°F or dropping below 44°F only one day in ten.
Over the course of December, the length of the day is essentially constant. The shortest day of the month is December 14 with 9:40 hours of daylight; the longest day is December 1 with 9:49 hours of daylight.
The earliest sunrise is at 6:53am on December 1; the latest sunset is at 4:53pm on December 31; the latest sunrise is at 7:12am on December 29; the earliest sunset is at 4:42pm on December 4.
Daylight savings time is observed in 2012 but it neither starts nor ends in December, so the entire month is in standard time.
The median cloud cover ranges from 60% (partly cloudy) to 84% (mostly cloudy). The trend is for the sky to be becoming rapidly cloudier with the median cloud cover increasing by 24% from the start to the end of the month.
On December 1, the clearest day of the month, the sky is clear, mostly clear, or partly cloudy 53% of the time, and overcast or mostly cloudy 45% of the time.
On December 30, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 68% of the time, and clear or mostly clear 31% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around December 31, occurring in 34% of days. Precipitation is least likely around December 1, occurring in 28% of days.
Throughout December, the most common forms of precipitation are light rain, moderate rain, and drizzle.
Light rain is the most severe precipitation observed during 42% of those days with precipitation. It is most likely around December 10, when it is observed during 14% of all days.
Moderate rain is the most severe precipitation observed during 39% of those days with precipitation. It is most likely around December 27, when it is observed during 13% of all days.
Drizzle is the most severe precipitation observed during 12% of those days with precipitation. It is most likely around December 31, when it is observed during 4% of all days.
Either snow is exceptionally unlikely to fall at this location in December or this station does not reliably report precipitation types.
The relative humidity typically ranges from 54% (mildly humid) to 95% (very humid) over the course of a typical December, rarely dropping below 33% (comfortable) and reaching as high as 100% (very humid).
The air is driest around December 1, at which time the relative humidity drops below 65% (mildly humid) three days out of four; it is most humid around December 15, rising above 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 typical December, the dew point typically varies from 35°F (dry) to 45°F (dry) and is rarely below 27°F (dry) or above 52°F (very comfortable).
Over the course of December typical wind speeds vary from 0 mph to 9 mph (calm to gentle breeze), rarely exceeding 15 mph (moderate breeze).
The highest average wind speed of 4 mph (light breeze) occurs around December 28, at which time the average daily maximum wind speed is 9 mph (gentle breeze).
The lowest average wind speed of 4 mph (light breeze) occurs around December 2, at which time the average daily maximum wind speed is 8 mph (gentle breeze).