September Weather in Charleston, United States

Last updated: June 24, 2025

In September, the average temperature in Charleston, United States is a pleasant 21°C (70°F). However, temperatures can vary significantly, with a minimum of 7°C (45°F) and a maximum reaching up to 36°C (96°F). Visitors should also prepare for precipitation, which averages 103 mm (4.0 in) over approximately 8 days, paired with an average humidity of 73%.

September Temperature in Charleston

In September in Charleston, the average temperature is 21°C (70°F). The maximum can reach 36°C (96°F), while the minimum can drop as low as 7°C (45°F). This diverse temperature range makes it an ideal time for travelers seeking both warm days and cooler nights.

September Weather in Charleston: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Charleston, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Charleston, September typically has an average temperature of 21°C (70°F), with highs reaching up to 36°C (96°F) and lows dropping to around 7°C (45°F).

Data source: Temperature data for Charleston generated using information from the Copernicus Climate Change Service.

September Precipitation in Charleston

In Charleston in September, the precipitation amount is 103 mm (4.0 in) over a span of 8 days.

September Precipitation Trends in Charleston

The chart displays monthly precipitation patterns in Charleston, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Charleston, September typically receives around 103 mm (4.0 inches) of precipitation spread over approximately 8 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

September Humidity in Charleston

In Charleston in September, humidity is 73%. With an average temperature of 21°C (70°F), this humidity feels like a warm embrace that can make outdoor activities feel sweltering, so it's essential to stay hydrated and take breaks in the shade while exploring.

September Average Humidity in Charleston

This chart illustrates the average monthly humidity levels in Charleston, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Charleston is approximately 73%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Charleston

In Charleston in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Charleston.

Maximum UV Index Levels in Charleston for September

The chart shows the monthly maximum UV Index (UVI) for Charleston in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Charleston typically reaches 8, which falls under the very high exposure category.

Data source: Charleston September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How September Weather in Charleston Compares to Other Months

Weather in Charleston varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Charleston, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Charleston, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	2°C (37°F)	101 mm (4.0 inches)	88%	moderate
February Weather	5°C (42°F)	152 mm (6.0 inches)	88%	moderate
March Weather	9°C (48°F)	119 mm (4.7 inches)	88%	high
April Weather	13°C (56°F)	134 mm (5.3 inches)	86%	very high
May Weather	19°C (66°F)	159 mm (6.3 inches)	82%	very high
June Weather	22°C (72°F)	154 mm (6.1 inches)	84%	very high
July Weather	25°C (77°F)	124 mm (4.9 inches)	82%	very high
August Weather	23°C (74°F)	114 mm (4.5 inches)	73%	very high
September Weather	21°C (70°F)	103 mm (4.0 inches)	73%	very high
October Weather	16°C (61°F)	117 mm (4.6 inches)	81%	high
November Weather	8°C (46°F)	78 mm (3.1 inches)	89%	moderate
December Weather	5°C (41°F)	124 mm (4.9 inches)	86%	moderate