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September Weather in Williamstown, United States

Last updated: June 24, 2025

In September, the average temperature in Williamstown, United States hovers around 17°C (62°F). However, prepare for a range as the minimum can dip to -1°C (30°F) and the maximum may soar up to 31°C (88°F). Expect about 105 mm (4.1 in) of precipitation spread over 10 days, contributing to an average humidity of 72%.

September Temperature in Williamstown

In September in Williamstown, the average temperature is 17°C (62°F). The maximum can reach 31°C (88°F) and the minimum can be as low as -1°C (30°F). It's a great time to visit if you enjoy a range of temperatures and want to experience both warm days and cooler nights.

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

The chart illustrates September temperature patterns in Williamstown, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Williamstown, September typically has an average temperature of 17°C (62°F), with highs reaching up to 31°C (88°F) and lows dropping to around -1°C (30°F).
JanFebMarAprMayJunJulAugSepOctNovDec232632445665706962513628
Data source: Temperature data for Williamstown 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 Williamstown

In Williamstown in September, the precipitation amount is 105 mm (4.1 in) over the course of 10 days.

September Precipitation Trends in Williamstown

The chart displays monthly precipitation patterns in Williamstown, 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 Williamstown, September typically receives around 105 mm (4.1 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec861059413611090130103105155114115
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Williamstown

In Williamstown in September humidity is 72%. With an average temperature of 17°C (62°F), this humidity feels like a warm embrace, making it perfect for leisurely strolls but potentially heavy on the skin, prompting travelers to seek shade during midday excursions.

September Average Humidity in Williamstown

This chart illustrates the average monthly humidity levels in Williamstown, 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 Williamstown is approximately 72%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec90%88%86%84%76%72%67%64%72%81%87%85%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Williamstown

In Williamstown in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Williamstown.

Maximum UV Index Levels in Williamstown for September

The chart shows the monthly maximum UV Index (UVI) for Williamstown 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 Williamstown typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34681010997642
Data source: Williamstown 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 Williamstown Compares to Other Months

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

This table compares monthly weather conditions in Williamstown, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (23°F)86 mm (3.4 inches)89%moderate
February Weather-3°C (26°F)105 mm (4.1 inches)88%moderate
March Weather0°C (32°F)94 mm (3.7 inches)86%high
April Weather7°C (44°F)136 mm (5.4 inches)84%very high
May Weather13°C (56°F)110 mm (4.3 inches)76%very high
June Weather18°C (65°F)90 mm (3.5 inches)72%very high
July Weather21°C (71°F)130 mm (5.1 inches)66%very high
August Weather20°C (69°F)103 mm (4.0 inches)64%very high
September Weather17°C (62°F)105 mm (4.1 inches)72%high
October Weather10°C (51°F)155 mm (6.1 inches)81%high
November Weather2°C (37°F)113 mm (4.5 inches)87%moderate
December Weather-2°C (28°F)115 mm (4.5 inches)84%low

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