The hottest month in Charleston County is July when the average maximum temperature is 32°, average temperature is 28° and average minimum temperature is 24°.
The coolest month in Charleston County is January when the average maximum temperature is 15°, average temperature is 10° and average minimum temperature is 5°.
The longest days in Charleston County are in June, with an average of 14.3 hours of daylight per day. December has the shortest days with an average of 10 hours of daylight per day.
The sunniest days in Charleston County are in July which has the most hours of sunshine per day with an average of 9.3 hours of sunshine per day, making it a sunny month with few clouds. January has the least sunshine with an average of 6.3 hours of sunshine per day, making it a quite sunny month with some cloud cover.
The ultraviolet index is the highest in July when it reaches 11.2 and lowest in December when it reaches 3.2.
An ultraviolet index reading above 11 indicates an extreme risk of harm from unprotected sun exposure. Unprotected skin risks burning in less than 10 minutes. Take all precautions because unprotected skin and eyes can burn in minutes. Tanning will be safest before 10am and after 4pm but only with a good application of sun screen. For those with sensitive skin stay in the shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days. Watch out for relections from water that may increase ultraviolet exposure.
The warmest sea water temperatures in Charleston County are found in August when they peak at 28° and lowest in March when they dip to 20°.
The sea is best for swimming between June and December when the temperature is above 24° which is warm and pleasant for relaxing and swimming for long periods.
The wettest month in Charleston County is June with 72.8cm of rain and August has the most days of rain with 10.8 days with some rain, a wet time to visit the beach.
The driest month in Charleston County is April with 20.2cm of rain and October has the fewest days of rain with 6.8 days with some rain, a slightly wet time to visit the beach.
The most humid month in Charleston County is August with a dew point (an indicator of humidity) of 26° which is very uncomfortable and fairly oppressive unless you are on a beach. At night you would most likely require airconditioning.
The least humid month in Charleston County is January with a dew point of 8° which is a bit dry for some.
The most windy month in Charleston County is April when the average maximum windspeed is 27kmh and the average wind speed is 12kmh.
The least windy month in Charleston County is September when the average maximum windspeed is 21kmh and the average wind speed is 8kmh.