September Weather in Williamsport, United States

Last updated: June 24, 2025

In Williamsport, United States, the average temperature in September hovers around 21°C (70°F), offering a pleasant climate for visitors. Expect temperatures to dip as low as 6°C (42°F) and rise to a maximum of 34°C (93°F). During this month, you'll encounter an average precipitation of 67 mm (2.6 in), typically spread over 7 days, with humidity levels around 78%, making it a bit muggy at times.

September Temperature in Williamsport

In September in Williamsport, the average temperature is 21°C (70°F), with maximums reaching 34°C (93°F) and minimums dropping as low as 6°C (42°F). This pleasant climate makes Williamsport an ideal destination for travelers seeking a comfortable getaway.

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 34°C (93°F) and lows dropping to around 6°C (42°F).

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

September Precipitation in Williamsport

In Williamsport in September, the total precipitation amount is 67 mm (2.6 in) over a span of 7 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 67 mm (2.6 inches) of precipitation spread over approximately 7 days.

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

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Williamsport

In Williamsport in September, humidity is 78%. With an average temperature of 21°C (70°F), this humidity feels like a warm, enveloping blanket that can leave travelers feeling sticky and slightly fatigued, making it important to stay hydrated and take frequent breaks from outdoor activities.

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 78%, 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 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.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	-2°C (29°F)	76 mm (3.0 inches)	85%	moderate
February Weather	0°C (32°F)	77 mm (3.1 inches)	85%	moderate
March Weather	6°C (42°F)	112 mm (4.4 inches)	86%	high
April Weather	11°C (52°F)	104 mm (4.1 inches)	87%	very high
May Weather	18°C (64°F)	151 mm (5.9 inches)	81%	very high
June Weather	23°C (74°F)	103 mm (4.0 inches)	82%	extreme
July Weather	25°C (77°F)	93 mm (3.7 inches)	81%	very high
August Weather	23°C (74°F)	106 mm (4.2 inches)	79%	very high
September Weather	21°C (70°F)	67 mm (2.6 inches)	78%	very high
October Weather	14°C (58°F)	116 mm (4.6 inches)	81%	high
November Weather	5°C (42°F)	76 mm (3.0 inches)	89%	moderate
December Weather	2°C (36°F)	61 mm (2.4 inches)	86%	low