September weather forecast
Charleston, SC

Trees along both sides of a street in Charleston, South Carolina
Trees along both sides of a street in Charleston, South Carolina

Weather in September

The first month of the autumn, September, is still a warm month in Charleston, South Carolina, with an average temperature fluctuating between 83.5°F (28.6°C) and 73°F (22.8°C).

Temperature

In September, the average high-temperature is essentially the same as in August - a moderately hot 83.5°F (28.6°C). The average low-temperature, in September, is 73°F (22.8°C).

Heat index

In September, the average heat index is computed to be a hot 90.9°F (32.7°C). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Take into consideration that the heat index values are calculated for shade and light wind conditions. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature', 'real feel', 'felt air temperature', or 'feels like', combines air temperature and relative humidity to represent a human perceived temperature equivalent. This effect is subjective, depending on the activity and individual's heat perception influenced by various reasons (clothing, metabolic differences, differences in body mass, height, and shape). Be aware that direct exposure to sunlight increases heat impact and may raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly important for children. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.

Humidity

In Charleston, the average relative humidity in September is 75%.

Rainfall

In Charleston, during September, the rain falls for 18.4 days and regularly aggregates up to 5" (127mm) of precipitation. Throughout the year, there are 178.9 rainfall days, and 41.93" (1065mm) of precipitation is accumulated.

Snowfall

In Charleston, snow does not fall in February through November.

Ocean temperature

In Charleston, in September, the average water temperature is 81.7°F (27.6°C).
Note: For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

Daylight

The average length of the day in September in Charleston is 12h and 22min.
On the first day of September, sunrise is at 6:54 am and sunset at 7:44 pm. On the last day of the month, sunrise is at 7:13 am and sunset at 7:05 pm EDT.

Sunshine

In September, the average sunshine in Charleston is 9.1h.

UV index

In Charleston, the average daily maximum UV index in September is 6. A UV Index estimate of 6 to 7 represents a high health risk from unprotected exposure to Sun's UV rays for the average person.
Note: The average daily UV index of 6 in September transform into the following instructions:
Take precautions and adopt sun safety practices. Protection against sunburn is obliged. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. A wide-brim hat offers excellent sun protection for the eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. Beware! The strength of the UV rays is significantly increased by the reflection of the water and sand.
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FAQ

What is the temperature in September in Charleston?

The average high-temperature, in September, in Charleston, is 83.5°F (28.6°C), while the average low-temperature is 73°F (22.8°C). In September, the average heat index (a.k.a. 'real feel', 'feels like'), which combines air temperature and relative humidity, is computed to be 90.9°F (32.7°C).

What is the average humidity in September in Charleston?

The average relative humidity in September in Charleston, South Carolina, is 75%.

How much does it rain in Charleston in September?

In Charleston, South Carolina, in September, during 18.4 rainfall days, 5" (127mm) of precipitation is typically accumulated.

When it does not snow in Charleston?

February through November are months without snowfall in Charleston, South Carolina.

How warm is the water in September in Charleston?

In Charleston, the average seawater temperature in September is 81.7°F (27.6°C). For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

What is the average length of the day in September in Charleston?

In Charleston, South Carolina, the average day length in September is 12h and 22min.

When is the sunrise / sunset in September in Charleston?

On the first day of September in Charleston, South Carolina, sunrise is at 6:54 am and sunset at 7:44 pm. On the last day of the month, sunrise is at 7:13 am and sunset at 7:05 pm EDT.

How long on average sun shines in September in Charleston?

In September, the average sunshine duration in Charleston is 9.1h.

How high is the UV index in September in Charleston?

In Charleston, South Carolina, the average daily maximum UV index in September is 6. A UV Index estimate of 6 to 7 represents a high health risk from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Charleston, SC

Average temperature in September - Charleston, SC
  • Average high temperature in September: 83.5°F

The warmest month (with the highest average high temperature) is July (88.2°F).
The month with the lowest average high temperature is January (57°F).

  • Average low temperature in September: 73°F

The month with the highest average low temperature is July (77.4°F).
The coldest month (with the lowest average low temperature) is January (44.4°F).

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Average pressure in September
Charleston, SC

Average pressure in September - Charleston, SC
  • Average pressure in September: 30"Hg

The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.98"Hg).

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Average wind speed in September
Charleston, SC

Average wind speed in September - Charleston, SC
  • Average wind speed in September: 8.3mph

The windiest month (with the highest average wind speed) is April (9.4mph).
The calmest month (with the lowest average wind speed) is August (7.5mph).

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Average humidity in September
Charleston, SC

Average humidity in September - Charleston, SC
  • Average humidity in September: 75%

The month with the highest relative humidity is December (78%).
The months with the lowest relative humidity are January and March (73%).

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Average rainfall in September
Charleston, SC

Average rainfall in September - Charleston, SC
  • Average rainfall in September: 5"

The wettest month (with the highest rainfall) is August (7.13").
The driest month (with the least rainfall) is January (1.42").

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Average rainfall days in September
Charleston, SC

Average rainfall days in September - Charleston, SC
  • Average rainfall days in September: 18.4 days

The month with the highest number of rainy days is August (24.8 days).
The month with the least rainy days is November (8.7 days).

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Average snowfall in September
Charleston, SC

Average snowfall in September - Charleston, SC
  • Average snowfall in September: 0"

The month with the highest snowfall is January (0.12").
The months with the least snowfall are February, March, April, May, June, July, August, September, October and November (0").

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Average snowfall days in September
Charleston, SC

Average snowfall days in September - Charleston, SC
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (0.4 days).
The months with the least snowfall days are March, April, May, June, July, August, September, October and November (0 days).

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Average sea temperature in September
Charleston, SC

Average sea temperature in September - Charleston, SC
  • Average sea temperature in September: 81.7°F

The best month for swimming (with the highest average sea temperature) is August (83.5°F).
The coldest month (with the lowest average sea temperature) is February (61.9°F).

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Average daylight in September /
Average sunshine in September
Charleston, SC

Average daylight in September / Average sunshine in September - Charleston, SC
  • Average daylight in September: 12h and 22min

The month with the longest days is June (Average daylight: 14h and 17min).
The month with the shortest days is December (Average daylight: 10h and 2min).

  • Average sunshine in September: 9h and 6min

The month with the most sunshine is July (Average sunshine: 11h and 0min).
The month with the least sunshine is December (Average sunshine: 5h and 42min).

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Average sunshine days in September
Charleston, SC

Average sunshine days in September - Charleston, SC
  • Average sunshine days in September: 8.5 days

The month with the most sunshine days is January (19.3 days).
The month with the least sunshine days is August (3.8 days).

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Average UV index in September
Charleston, SC

Average UV index in September - Charleston, SC
  • Average UV index in September: 6

The months with the highest UV index are May, June, July and August (UV index 7).
The month with the lowest UV index is January (UV index 3).

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Average cloud cover in September
Charleston, SC

Average cloud cover in September - Charleston, SC
  • Average cloud cover in September: 29

The months with the most cloud cover are February and December (Cloud cover 39).
The months with the least cloud cover are June and July (Cloud cover 26).

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Average visibility in September
Charleston, SC

Average visibility in September - Charleston, SC
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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