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 year. 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%).
Over the course of a year, the temperature typically varies from 38°F to 90°F and is rarely below 26°F or above 95°F.
The warm season lasts from May 23 to September 19 with an average daily high temperature above 84°F. The hottest day of the year is July 19, with an average high of 90°F and low of 74°F.
The cold season lasts from December 3 to February 24 with an average daily high temperature below 64°F. The coldest day of the year is January 19, with an average low of 38°F and high of 58°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:59 hours of daylight; the longest day is June 20 with 14:19 hours of daylight.
The earliest sunrise is at 6:11am on June 10 and the latest sunset is at 8:33pm on June 30. The latest sunrise is at 7:40am on November 3 and the earliest sunset is at 5:13pm on December 4.
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 35% (mostly clear) to 57% (partly cloudy). The sky is cloudiest on January 8 and clearest on November 11. The clearer part of the year begins around March 8. The cloudier part of the year begins around December 8.
On November 11, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 64% of the time, and overcast or mostly cloudy 35% of the time.
On January 8, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 54% of the time, and clear or mostly clear 45% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around July 19, occurring in 56% of days. Precipitation is least likely around November 3, occurring in 31% of days.
Over the entire year, the most common forms of precipitation are thunderstorms, light rain, and moderate rain.
Thunderstorms are the most severe precipitation observed during 35% of those days with precipitation. They are most likely around July 18, when it is observed during 40% of all days.
Light rain is the most severe precipitation observed during 30% of those days with precipitation. It is most likely around January 11, when it is observed during 18% of all days.
Moderate rain is the most severe precipitation observed during 27% of those days with precipitation. It is most likely around January 8, when it is observed during 16% of all days.
During the warm season, which lasts from May 23 to September 19, there is a 50% 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 thunderstorms (62% of days with precipitation have at worst thunderstorms), moderate rain (17%), and light rain (17%).
During the cold season, which lasts from December 3 to February 24, there is a 39% 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 (44% of days with precipitation have at worst light rain), moderate rain (38%), drizzle (5%), and heavy rain (5%).
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 41% (comfortable) to 95% (very humid) over the course of the year, rarely dropping below 22% (dry) and reaching as high as 100% (very humid).
The air is driest around April 11, at which time the relative humidity drops below 50% (mildly humid) three days out of four; it is most humid around August 21, exceeding 92% (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 29°F (dry) to 76°F (very muggy) and is rarely below 11°F (dry) or above 79°F (oppressive).
There are two periods in the year that are most comfortable: The first is between March 2 and May 12 and the second is between October 6 and December 8. The air feels neither too dry nor too muggy during these periods.
Over the course of the year typical wind speeds vary from 0 mph to 17 mph (calm to moderate breeze), rarely exceeding 23 mph (fresh breeze).
The highest average wind speed of 10 mph (gentle breeze) occurs around April 6, at which time the average daily maximum wind speed is 17 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around August 17, at which time the average daily maximum wind speed is 13 mph (moderate breeze).