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September Weather in Charleston, United States

Last updated: June 24, 2025

In Charleston, United States, the average temperature in September hovers around 25°C (78°F). Daytime highs can reach up to 38°C (101°F), while nights can dip to a cool 12°C (54°F). Expect around 100 mm (3.9 in) of precipitation over the course of 7 days, with an average humidity of 73% adding to the tropical feel.

September Temperature in Charleston

In September in Charleston, the average temperature is 25°C (78°F). Maximums can reach 38°C (101°F), while minimums can drop to as low as 12°C (54°F). This makes Charleston an ideal destination for travelers seeking warm weather and diverse outdoor activities during this time.

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 25°C (78°F), with highs reaching up to 38°C (101°F) and lows dropping to around 12°C (54°F).
JanFebMarAprMayJunJulAugSepOctNovDec454958637279828177665249
Data source: Temperature data for Charleston generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Charleston

In Charleston in September, the precipitation amount is 100 mm (3.9 in) over a span of 7 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 100 mm (3.9 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec12019516814911513411212410011384143
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Charleston

In Charleston in September, humidity is 73%. With an average temperature of 25°C (78°F), this humidity feels like stepping into a warm, heavy blanket that wraps around you, making travel feel sluggish and requiring regular breaks to stay refreshed.

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.
JanFebMarAprMayJunJulAugSepOctNovDec84%83%80%82%83%80%80%75%73%76%84%88%
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 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check 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 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec47810111111109764
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.
 TemperaturePrecipitationHumidityUV
January Weather7°C (45°F)120 mm (4.7 inches)84%moderate
February Weather10°C (49°F)195 mm (7.7 inches)83%high
March Weather14°C (58°F)168 mm (6.6 inches)80%very high
April Weather17°C (63°F)149 mm (5.9 inches)82%very high
May Weather22°C (73°F)115 mm (4.5 inches)83%extreme
June Weather26°C (79°F)134 mm (5.3 inches)80%extreme
July Weather28°C (82°F)112 mm (4.4 inches)80%extreme
August Weather27°C (81°F)124 mm (4.9 inches)75%very high
September Weather25°C (78°F)100 mm (3.9 inches)73%very high
October Weather19°C (67°F)113 mm (4.5 inches)76%high
November Weather11°C (53°F)84 mm (3.3 inches)84%high
December Weather10°C (50°F)143 mm (5.6 inches)88%moderate

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