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September Weather in Watertown, United States

Last updated: June 24, 2025

In September, the average temperature in Watertown, United States reaches a pleasant 26°C (80°F), with daily fluctuations ranging from a cool 16°C (61°F) to a warm 37°C (99°F). Visitors should be prepared for the 140 mm (5.5 in) of precipitation over 14 days, contributing to an average humidity level of 83%. It's a month that beautifully balances warmth and moisture, enhancing the region's lush landscape.

September Temperature in Watertown

In September, in Watertown, the average temperature is 26°C (80°F). Maximums can reach 37°C (99°F), and minimums can be as low as 16°C (61°F). This pleasant climate makes Watertown an ideal destination for travelers looking to enjoy warm weather activities.

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 26°C (80°F), with highs reaching up to 37°C (99°F) and lows dropping to around 16°C (61°F).
JanFebMarAprMayJunJulAugSepOctNovDec556164697679818179746258
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 140 mm (5.5 in) over the course of 14 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 140 mm (5.5 inches) of precipitation spread over approximately 14 days.
JanFebMarAprMayJunJulAugSepOctNovDec54733675761581751841406564103
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 83%. With an average temperature of 26°C (80°F), this humidity feels like a warm, enveloping blanket that can make traveling quite uncomfortable; you may find yourself needing frequent breaks for hydration and cool shade as the thick air clings to your skin.

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 83%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%82%80%76%73%74%80%79%83%77%84%88%
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 reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check 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 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec579101111111110865
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 Weather13°C (55°F)54 mm (2.1 inches)85%moderate
February Weather16°C (61°F)73 mm (2.9 inches)82%high
March Weather18°C (65°F)36 mm (1.4 inches)80%very high
April Weather21°C (70°F)75 mm (3.0 inches)76%very high
May Weather24°C (76°F)76 mm (3.0 inches)73%extreme
June Weather26°C (80°F)158 mm (6.2 inches)74%extreme
July Weather27°C (81°F)175 mm (6.9 inches)80%extreme
August Weather27°C (81°F)184 mm (7.2 inches)79%extreme
September Weather26°C (80°F)140 mm (5.5 inches)83%very high
October Weather23°C (74°F)65 mm (2.6 inches)77%very high
November Weather17°C (62°F)64 mm (2.5 inches)84%high
December Weather14°C (58°F)103 mm (4.1 inches)88%moderate

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