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September Weather in Williamsport, United States

Last updated: June 24, 2025

In September, the average temperature in Williamsport, United States is a pleasant 21°C (70°F), with minimums dipping to 6°C (43°F) and peaking at a warm 35°C (96°F). Expect approximately 91 mm (3.6 in) of precipitation over 8 days, contributing to a humidity level of 73% that creates a rich, refreshing atmosphere.

September Temperature in Williamsport

In September in Williamsport, the average temperature is 21°C (70°F), with maximums reaching up to 35°C (96°F) and minimums dropping as low as 6°C (43°F). This pleasant climate makes Williamsport an ideal destination for travelers seeking a mix of warm days and cooler nights.

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

The chart illustrates September temperature patterns in Williamsport, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Williamsport, September typically has an average temperature of 21°C (70°F), with highs reaching up to 35°C (96°F) and lows dropping to around 6°C (43°F).
JanFebMarAprMayJunJulAugSepOctNovDec323644536572777470594338
Data source: Temperature data for Williamsport 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 Williamsport

In Williamsport in September, the total precipitation amount is 91 mm (3.6 in) over the course of 8 days.

September Precipitation Trends in Williamsport

The chart displays monthly precipitation patterns in Williamsport, 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 Williamsport, September typically receives around 91 mm (3.6 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec81110123126127130109919110296104
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Williamsport

In Williamsport 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 Williamsport

This chart illustrates the average monthly humidity levels in Williamsport, 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 Williamsport is approximately 73%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%88%87%85%81%82%81%73%73%78%89%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Williamsport

In Williamsport 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 Williamsport.

Maximum UV Index Levels in Williamsport for September

The chart shows the monthly maximum UV Index (UVI) for Williamsport 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 Williamsport typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910101098643
Data source: Williamsport 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 Williamsport Compares to Other Months

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

This table compares monthly weather conditions in Williamsport, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather0°C (33°F)81 mm (3.2 inches)88%moderate
February Weather2°C (37°F)109 mm (4.3 inches)88%moderate
March Weather7°C (44°F)123 mm (4.8 inches)87%high
April Weather12°C (53°F)126 mm (5.0 inches)85%very high
May Weather18°C (65°F)127 mm (5.0 inches)81%very high
June Weather22°C (73°F)130 mm (5.1 inches)82%very high
July Weather25°C (77°F)109 mm (4.3 inches)81%very high
August Weather24°C (75°F)91 mm (3.6 inches)73%very high
September Weather21°C (70°F)91 mm (3.6 inches)73%very high
October Weather15°C (59°F)102 mm (4.0 inches)78%high
November Weather6°C (43°F)96 mm (3.8 inches)89%moderate
December Weather3°C (38°F)104 mm (4.1 inches)87%moderate

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