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September Weather in Harleysville, United States

Last updated: June 24, 2025

In September, the average temperature in Harleysville, United States hovers around 21°C (69°F). Expect fluctuations, with temperatures dipping to a cool 5°C (41°F) and soaring up to a sizzling 34°C (94°F). During this time, anticipate about 100 mm (4.0 in) of precipitation spread over 9 days, contributing to an average humidity of 66%.

September Temperature in Harleysville

In September in Harleysville, the average temperature is 21°C (69°F), with maximums reaching 34°C (94°F) and minimums dropping as low as 5°C (41°F). This makes it a great time for travelers to enjoy a variety of outdoor activities while being prepared for some temperature fluctuations.

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

The chart illustrates September temperature patterns in Harleysville, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Harleysville, September typically has an average temperature of 21°C (69°F), with highs reaching up to 34°C (94°F) and lows dropping to around 5°C (41°F).
JanFebMarAprMayJunJulAugSepOctNovDec343742536372777569594538
Data source: Temperature data for Harleysville 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 Harleysville

In Harleysville in September, the precipitation amount is 100 mm (4.0 in) over the course of 9 days.

September Precipitation Trends in Harleysville

The chart displays monthly precipitation patterns in Harleysville, 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 Harleysville, September typically receives around 100 mm (4.0 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec6710610510414411114716310010286101
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Harleysville

In Harleysville in September humidity is 66%. With an average temperature of 21°C (69°F), this humidity feels like a warm embrace, making it a bit sticky, but still comfortable for traveling as long as you stay hydrated and take breaks in the shade.

September Average Humidity in Harleysville

This chart illustrates the average monthly humidity levels in Harleysville, 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 Harleysville is approximately 66%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec87%85%85%83%75%74%65%62%66%79%87%85%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Harleysville

In Harleysville 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 Harleysville.

Maximum UV Index Levels in Harleysville for September

The chart shows the monthly maximum UV Index (UVI) for Harleysville 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 Harleysville typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910101098642
Data source: Harleysville 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 Harleysville Compares to Other Months

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

This table compares monthly weather conditions in Harleysville, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather1°C (34°F)67 mm (2.7 inches)87%moderate
February Weather3°C (37°F)106 mm (4.2 inches)85%moderate
March Weather6°C (43°F)105 mm (4.1 inches)85%high
April Weather12°C (53°F)104 mm (4.1 inches)83%very high
May Weather17°C (63°F)144 mm (5.7 inches)75%very high
June Weather22°C (72°F)111 mm (4.4 inches)73%very high
July Weather25°C (78°F)147 mm (5.8 inches)65%very high
August Weather24°C (75°F)163 mm (6.4 inches)62%very high
September Weather21°C (69°F)100 mm (4.0 inches)66%very high
October Weather15°C (60°F)102 mm (4.0 inches)79%high
November Weather7°C (45°F)86 mm (3.4 inches)87%moderate
December Weather3°C (38°F)101 mm (4.0 inches)85%low

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