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September Weather in Watertown, United States

Last updated: June 24, 2025

In Watertown, United States, the average temperature in September hovers around 17°C (63°F). However, be prepared for a range of temperatures, as it can dip to a chilly 3°C (38°F) or soar to a balmy 30°C (86°F). You can expect about 78 mm (3.1 in) of precipitation spread over 9 days, and with an average humidity of 78%, the air will feel quite muggy.

September Temperature in Watertown

In September in Watertown, the average temperature is 17°C (63°F). Maximum temperatures can reach 30°C (86°F), while minimums can drop as low as 3°C (38°F). Travelers should be prepared for a range of weather conditions, from warm days to cool nights.

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 17°C (63°F), with highs reaching up to 30°C (86°F) and lows dropping to around 3°C (38°F).
JanFebMarAprMayJunJulAugSepOctNovDec232532435565727063523930
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 78 mm (3.1 in) over the course 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 78 mm (3.1 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec9388861231039714510878160127108
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 78%. With an average temperature of 17°C (63°F), this humidity feels like a warm, enveloping blanket, making traveling slightly uncomfortable as you navigate the sticky air, prompting the need for frequent breaks in cooler, shaded areas.

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 78%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec90%90%87%88%82%79%78%76%78%84%89%86%
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 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 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 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec246899997532
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-5°C (23°F)93 mm (3.7 inches)90%low
February Weather-4°C (25°F)88 mm (3.5 inches)90%moderate
March Weather0°C (32°F)86 mm (3.4 inches)87%high
April Weather6°C (43°F)123 mm (4.9 inches)88%very high
May Weather13°C (56°F)103 mm (4.1 inches)82%very high
June Weather18°C (65°F)97 mm (3.8 inches)79%very high
July Weather22°C (72°F)145 mm (5.7 inches)78%very high
August Weather21°C (70°F)107 mm (4.2 inches)76%very high
September Weather17°C (63°F)78 mm (3.1 inches)78%high
October Weather11°C (53°F)160 mm (6.3 inches)84%moderate
November Weather4°C (39°F)127 mm (5.0 inches)89%moderate
December Weather-1°C (30°F)108 mm (4.2 inches)86%low

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