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September Weather in Charlestown, United States

Last updated: June 24, 2025

In September, the average temperature in Charlestown, United States is a pleasant 22°C (72°F). You can expect a minimum of 8°C (46°F) and a maximum of 35°C (96°F) throughout the month. Be prepared for some rain, with precipitation totaling around 104 mm (4.1 in) spread over 8 days. The average humidity is around 69%, making for a comfortable, if slightly moist, atmosphere!

September Temperature in Charlestown

In September in Charlestown, the average temperature is 22°C (72°F). Maximums can reach 35°C (96°F), and minimums can be as low as 8°C (46°F). This varied climate makes it a perfect destination for travelers seeking both warmth and cooler evenings.

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

The chart illustrates September temperature patterns in Charlestown, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Charlestown, September typically has an average temperature of 22°C (72°F), with highs reaching up to 35°C (96°F) and lows dropping to around 8°C (46°F).
JanFebMarAprMayJunJulAugSepOctNovDec353947556775787671604540
Data source: Temperature data for Charlestown 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 Charlestown

In Charlestown, in September, the precipitation amount is 104 mm (4.1 in) over a span of 8 days.

September Precipitation Trends in Charlestown

The chart displays monthly precipitation patterns in Charlestown, 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 Charlestown, September typically receives around 104 mm (4.1 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec8512013413712814595961059992104
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Charlestown

In Charlestown in September, humidity is 69%. With an average temperature of 22°C (72°F), this humidity feels like a warm, enveloping blanket, making travel feel sticky and slightly oppressive, yet also invigorating as the air is thick with the scent of blooming flora and vibrant surroundings.

September Average Humidity in Charlestown

This chart illustrates the average monthly humidity levels in Charlestown, 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 Charlestown is approximately 69%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec87%85%86%84%79%82%79%70%69%76%88%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Charlestown

In Charlestown 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 Charlestown.

Maximum UV Index Levels in Charlestown for September

The chart shows the monthly maximum UV Index (UVI) for Charlestown 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 Charlestown typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3579101110108743
Data source: Charlestown 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 Charlestown Compares to Other Months

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

This table compares monthly weather conditions in Charlestown, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather1°C (35°F)85 mm (3.3 inches)87%moderate
February Weather4°C (39°F)120 mm (4.7 inches)85%moderate
March Weather8°C (47°F)134 mm (5.3 inches)86%high
April Weather13°C (56°F)137 mm (5.4 inches)84%very high
May Weather19°C (67°F)128 mm (5.1 inches)79%very high
June Weather24°C (75°F)145 mm (5.7 inches)82%extreme
July Weather26°C (78°F)95 mm (3.8 inches)79%very high
August Weather24°C (76°F)96 mm (3.8 inches)70%very high
September Weather22°C (72°F)104 mm (4.1 inches)69%very high
October Weather16°C (60°F)99 mm (3.9 inches)76%high
November Weather7°C (45°F)92 mm (3.6 inches)88%moderate
December Weather5°C (40°F)104 mm (4.1 inches)87%moderate

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