This report describes the typical weather at the Catalina Airport (Avalon/Santa Catalina Island, California, United States) weather station over the course of an average December. It is based on the historical records from 2000 to 2012. Earlier records are either unavailable or unreliable.
Avalon/Santa Catalina Island, California has a cold desert climate. The area within 25 mi of this station is covered by oceans and seas (96%) and shrublands (4%).
The month of December is characterized by essentially constant daily high temperatures, with daily highs around 60°F throughout the month, exceeding 70°F or dropping below 51°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 24 with 9:56 hours of daylight; the longest day is December 2 with 10:05 hours of daylight.
The earliest sunrise is at 6:41am on December 1; the latest sunset is at 4:57pm on December 31; the latest sunrise is at 6:57am on December 31; the earliest sunset is at 4:45pm 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 is 8% (clear) and does not vary substantially over the course of the month.
On December 16, a representative day, the sky is clear or mostly clear 67% of the time, partly cloudy 2% of the time, and mostly cloudy or overcast 27% of the time.
The average probability that some form of precipitation will be observed in a given day is 23%, with little variation over the course of the month.
Throughout December, the most common forms of precipitation are light rain, moderate rain, and heavy rain.
Light rain is the most severe precipitation observed during 55% of those days with precipitation. It is most likely around December 1, when it is observed during 14% of all days.
Moderate rain is the most severe precipitation observed during 31% of those days with precipitation. It is most likely around December 29, when it is observed during 8% of all days.
Heavy rain is the most severe precipitation observed during 13% of those days with precipitation. It is most likely around December 27, 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 37% (comfortable) to 80% (humid) over the course of a typical December, rarely dropping below 12% (very dry) and reaching as high as 100% (very humid).
The air is driest around December 3, at which time the relative humidity drops below 52% (mildly humid) three days out of four; it is most humid around December 12, rising above 66% (mildly 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 26°F (dry) to 45°F (dry) and is rarely below 8°F (dry) or above 53°F (very comfortable).
Over the course of December typical wind speeds vary from 0 mph to 13 mph (calm to moderate breeze), rarely exceeding 23 mph (fresh breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around December 17, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around December 3, at which time the average daily maximum wind speed is 13 mph (moderate breeze).