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 April. 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 April is characterized by rising daily high temperatures, with daily highs increasing from 72°F to 79°F over the course of the month, exceeding 87°F or dropping below 63°F only one day in ten.
Over the course of April, the length of the day is gradually increasing. From the start to the end of the month, the length of the day increases by 55 minutes, implying an average day-over-day increase of 1.8 minutes.
The shortest day of the month is April 1 with 12:34 hours of daylight; the longest day is April 30 with 13:29 hours of daylight.
The earliest sunrise is at 6:34am on April 30; the latest sunset is at 8:02pm on April 30; the latest sunrise is at 7:07am on April 1; the earliest sunset is at 7:41pm on April 1.
Daylight savings time is observed in 2012 but it neither starts nor ends in April, so the entire month is in daylight time.
The median cloud cover is 40% (mostly clear) and does not vary substantially over the course of the month.
On April 15, a representative day, the sky is clear or mostly clear 49% of the time, partly cloudy 15% of the time, and mostly cloudy or overcast 35% of the time.
The average probability that some form of precipitation will be observed in a given day is 33%, with little variation over the course of the month.
Throughout April, the most common forms of precipitation are light rain, thunderstorms, and moderate rain.
Light rain is the most severe precipitation observed during 35% of those days with precipitation. It is most likely around April 1, when it is observed during 13% of all days.
Thunderstorms are the most severe precipitation observed during 31% of those days with precipitation. They are most likely around April 30, when it is observed during 13% of all days.
Moderate rain is the most severe precipitation observed during 28% of those days with precipitation. It is most likely around April 1, when it is observed during 10% of all days.
Either snow is exceptionally unlikely to fall at this location in April or this station does not reliably report precipitation types.
The relative humidity typically ranges from 41% (comfortable) to 93% (very humid) over the course of a typical April, rarely dropping below 23% (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 April 29, rising above 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 typical April, the dew point typically varies from 42°F (dry) to 62°F (mildy humid) and is rarely below 26°F (dry) or above 70°F (muggy).
The time of the month between April 1 and April 30 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of April typical wind speeds vary from 2 mph to 17 mph (light air 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 9 mph (gentle breeze) occurs around April 27, at which time the average daily maximum wind speed is 16 mph (moderate breeze).