Average Weather in Charleston South Carolina, United States
In Charleston, the summers are hot and oppressive, the winters are cold and windy, and it is wet and partly cloudy year round. Over the course of the year, the temperature typically varies from 43°F to 89°F and is rarely below 30°F or above 94°F.
Based on the tourism score, the best times of year to visit Charleston for warm-weather activities are from mid April to late May and from late September to late October.
The hot season lasts for 3.7 months, from May 27 to September 17, with an average daily high temperature above 83°F. The hottest day of the year is July 23, with an average high of 89°F and low of 77°F.
The cool season lasts for 3.0 months, from December 2 to March 2, with an average daily high temperature below 65°F. The coldest day of the year is January 17, with an average low of 43°F and high of 59°F.
Average High and Low Temperature
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
In Charleston, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Charleston begins around September 12 and lasts for 3.1 months, ending around December 15. On October 27, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 66% of the time, and overcast or mostly cloudy 34% of the time.
The cloudier part of the year begins around December 15 and lasts for 8.9 months, ending around September 12. On July 27, the cloudiest day of the year, the sky is overcast or mostly cloudy 57% of the time, and clear, mostly clear, or partly cloudy 43% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Charleston varies significantly throughout the year.
The wetter season lasts 3.4 months, from June 4 to September 18, with a greater than 35% chance of a given day being a wet day. The chance of a wet day peaks at 51% on July 30.
The drier season lasts 8.6 months, from September 18 to June 4. The smallest chance of a wet day is 19% on October 30.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 51% on July 30.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Charleston experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Charleston. The most rain falls during the 31 days centered around August 19, with an average total accumulation of 5.2 inches.
The least rain falls around November 11, with an average total accumulation of 2.3 inches.
Average Monthly Rainfall
The length of the day in Charleston varies significantly over the course of the year. In 2021, the shortest day is December 21, with 10 hours, 0 minutes of daylight; the longest day is June 20, with 14 hours, 19 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 6:11 AM on June 11, and the latest sunrise is 1 hour, 31 minutes later at 7:42 AM on November 6. The earliest sunset is at 5:13 PM on December 4, and the latest sunset is 3 hours, 19 minutes later at 8:31 PM on June 29.
Daylight saving time (DST) is observed in Charleston during 2021, starting in the spring on March 14, lasting 7.8 months, and ending in the fall on November 7.
Sunrise & Sunset with Twilight and Daylight Saving Time
The figure below presents a compact representation of key lunar data for 2021. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.
Moon Rise, Set & Phases
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
Charleston experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 6.0 months, from April 27 to October 26, during which time the comfort level is muggy, oppressive, or miserable at least 26% of the time. The muggiest day of the year is July 21, with muggy conditions 99% of the time.
The least muggy day of the year is January 31, with muggy conditions 1% of the time.
Humidity Comfort Levels
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.
The average hourly wind speed in Charleston experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.2 months, from October 27 to May 2, with average wind speeds of more than 9.4 miles per hour. The windiest day of the year is February 26, with an average hourly wind speed of 10.9 miles per hour.
The calmer time of year lasts for 5.8 months, from May 2 to October 27. The calmest day of the year is August 17, with an average hourly wind speed of 7.8 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Charleston varies throughout the year.
The wind is most often from the west for 2.3 months, from January 7 to March 17, with a peak percentage of 36% on January 20. The wind is most often from the south for 5.3 months, from March 17 to August 26, with a peak percentage of 52% on July 19. The wind is most often from the north for 3.1 months, from October 5 to January 7, with a peak percentage of 36% on January 1.
Charleston is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average water temperature experiences some seasonal variation over the course of the year.
The time of year with warmer water lasts for 3.4 months, from June 14 to September 28, with an average temperature above 79°F. The day of the year with the warmest water is August 3, with an average temperature of 83°F.
The time of year with cooler water lasts for 4.0 months, from December 19 to April 21, with an average temperature below 67°F. The day of the year with the coolest water is March 6, with an average temperature of 63°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Charleston throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best times of year to visit Charleston for general outdoor tourist activities are from mid April to late May and from late September to late October, with a peak score in the first week of May.
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best times of year to visit Charleston for hot-weather activities are from mid May to early July and from mid August to late September, with a peak score in the first week of September.
For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.
Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.
Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.
Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.
Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.
Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).
The growing season in Charleston typically lasts for 10 months (308 days), from around February 15 to around December 20, rarely starting before January 22 or after March 12, and rarely ending before November 27 or after January 8.
Time Spent in Various Temperature Bands and the Growing Season
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.
Based on growing degree days alone, the first spring blooms in Charleston should appear around January 21, only rarely appearing before January 12 or after February 5.
Growing Degree Days
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy experiences significant seasonal variation over the course of the year.
The brighter period of the year lasts for 2.8 months, from April 7 to July 1, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is May 14, with an average of 6.7 kWh.
The darker period of the year lasts for 2.8 months, from November 11 to February 6, with an average daily incident shortwave energy per square meter below 3.6 kWh. The darkest day of the year is December 21, with an average of 2.8 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Charleston are 32.777 deg latitude, -79.931 deg longitude, and 20 ft elevation.
The topography within 2 miles of Charleston is essentially flat, with a maximum elevation change of 26 feet and an average elevation above sea level of 4 feet. Within 10 miles is also essentially flat (66 feet). Within 50 miles is essentially flat (509 feet).
The area within 2 miles of Charleston is covered by water (60%), artificial surfaces (27%), and herbaceous vegetation (12%), within 10 miles by artificial surfaces (33%) and water (33%), and within 50 miles by water (50%) and trees (27%).
This report illustrates the typical weather in Charleston, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Charleston.
For each station, the records are corrected for the elevation difference between that station and Charleston according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Charleston is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Charleston and a given station.
The stations contributing to this reconstruction are: Charleston NAS (60%, 8 kilometers, north) and Charleston Executive Airport (40%, 11 kilometers, southwest).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for airports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.
The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.
We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.