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September Weather in Watertown, United States

Last updated: June 24, 2025

In September, the average temperature in Watertown, United States hovers around 18°C (65°F). Expect a range with minimums dipping to 1°C (35°F) and maximums soaring up to 33°C (92°F). During this month, precipitation is about 99 mm (3.9 in) over approximately 9 days, contributing to an average humidity level of 79%.

September Temperature in Watertown

In September in Watertown, the average temperature is 18°C (65°F), with maximums that can reach 33°C (92°F) and minimums that can dip as low as 1°C (35°F). This makes it a great time to explore, so be sure to pack for both warm days and cooler evenings!

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

The chart illustrates September temperature patterns in Watertown, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Watertown, September typically has an average temperature of 18°C (65°F), with highs reaching up to 33°C (92°F) and lows dropping to around 1°C (35°F).
JanFebMarAprMayJunJulAugSepOctNovDec212335455970747165513629
Data source: Temperature data for Watertown 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 Watertown

In Watertown in September, the precipitation amount is 99 mm (3.9 in) during a span of 9 days.

September Precipitation Trends in Watertown

The chart displays monthly precipitation patterns in Watertown, 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 Watertown, September typically receives around 99 mm (3.9 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec51495710312111310294991144345
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Watertown

In Watertown in September, humidity is 79%. With an average temperature of 18°C (65°F), this humidity feels like walking through a warm mist, making traveling slightly uncomfortable and sticky, but offering a refreshing escape when you find moments of shade or a breeze.

September Average Humidity in Watertown

This chart illustrates the average monthly humidity levels in Watertown, 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 Watertown is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%85%85%85%78%80%78%76%79%83%88%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Watertown

In Watertown 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 Watertown.

Maximum UV Index Levels in Watertown for September

The chart shows the monthly maximum UV Index (UVI) for Watertown 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 Watertown typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34589101098532
Data source: Watertown 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 Watertown Compares to Other Months

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

This table compares monthly weather conditions in Watertown, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (22°F)51 mm (2.0 inches)85%moderate
February Weather-5°C (23°F)49 mm (1.9 inches)85%moderate
March Weather2°C (36°F)57 mm (2.3 inches)85%moderate
April Weather7°C (46°F)103 mm (4.1 inches)85%very high
May Weather15°C (59°F)121 mm (4.8 inches)78%very high
June Weather21°C (70°F)113 mm (4.5 inches)80%very high
July Weather23°C (74°F)102 mm (4.0 inches)78%very high
August Weather22°C (71°F)94 mm (3.7 inches)76%very high
September Weather18°C (65°F)99 mm (3.9 inches)79%very high
October Weather11°C (51°F)114 mm (4.5 inches)83%moderate
November Weather2°C (37°F)43 mm (1.7 inches)88%moderate
December Weather-2°C (30°F)45 mm (1.8 inches)81%low

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