This report describes the typical weather at the Charleston International Airport (Charleston Air Force Base) (Charleston, South Carolina, 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.
Charleston, South Carolina has a warm humid temperate climate with hot summers and no dry season. The area within 25 mi of this station is covered by forests (63%), oceans and seas (16%), croplands (12%), lakes and rivers (4%), and built-up areas (3%).
The month of December is characterized by falling daily high temperatures, with daily highs decreasing from 65°F to 59°F over the course of the month, exceeding 76°F or dropping below 46°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 26 with 9:59 hours of daylight; the longest day is December 1 with 10:08 hours of daylight.
The earliest sunrise is at 7:06am on December 1; the latest sunset is at 5:25pm on December 31; the latest sunrise is at 7:23am on December 30; the earliest sunset is at 5:13pm 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 44% (partly cloudy) to 54% (partly cloudy). The trend is for the sky to be becoming cloudier with the median cloud cover increasing by 9% from the start to the end of the month.
On December 16, a representative day, the sky is clear or mostly clear 46% of the time, partly cloudy 11% of the time, and mostly cloudy or overcast 41% 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 40% of days. Precipitation is least likely around December 1, occurring in 35% of days.
Throughout December, the most common forms of precipitation are light rain and moderate rain.
Light rain is the most severe precipitation observed during 45% of those days with precipitation. It is most likely around December 25, when it is observed during 18% of all days.
Moderate rain is the most severe precipitation observed during 39% of those days with precipitation. It is most likely around December 31, when it is observed during 15% 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 48% (comfortable) to 92% (very humid) over the course of a typical December, rarely dropping below 26% (dry) and reaching as high as 100% (very humid).
The air is driest around December 11, at which time the relative humidity drops below 61% (mildly humid) three days out of four; it is most humid around December 2, rising above 88% (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 32°F (dry) to 51°F (very comfortable) and is rarely below 13°F (dry) or above 67°F (muggy).
Over the course of December typical wind speeds vary from 1 mph to 14 mph (light air to moderate breeze), rarely exceeding 21 mph (fresh breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around December 31, at which time the average daily maximum wind speed is 14 mph (moderate breeze).
The lowest average wind speed of 8 mph (gentle breeze) occurs around December 2, at which time the average daily maximum wind speed is 13 mph (moderate breeze).