September Weather in Watertown, United States

Last updated: June 24, 2025

In September, the average temperature in Watertown, United States hovers around 18°C (64°F), with extremes ranging from a chilly 2°C (36°F) to a hot 33°C (91°F). Expect 113 mm (4.4 in) of precipitation over about 10 days, resulting in a high average humidity of 81%. Plan your activities accordingly to stay comfortable!

September Temperature in Watertown

In September in Watertown, the average temperature is 18°C (64°F). Maximums can reach 33°C (91°F), and minimums can be as low as 2°C (36°F). This makes Watertown a great destination for travelers looking to experience a range of temperatures, from warm days to cooler 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 18°C (64°F), with highs reaching up to 33°C (91°F) and lows dropping to around 2°C (36°F).

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

September Precipitation in Watertown

In Watertown in September, the total precipitation amount is 113 mm (4.4 in) over a span of 10 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 113 mm (4.4 inches) of precipitation spread over approximately 10 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 Watertown

In Watertown in September, humidity is 81%. With an average temperature of 18°C (64°F), this humidity feels like a warm embrace, making travel both refreshing and slightly stifling at the same time.

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 81%, 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 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.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	-9°C (16°F)	25 mm (1.0 inches)	87%	low
February Weather	-9°C (17°F)	29 mm (1.2 inches)	90%	moderate
March Weather	0°C (33°F)	54 mm (2.1 inches)	85%	moderate
April Weather	6°C (43°F)	83 mm (3.3 inches)	84%	high
May Weather	15°C (59°F)	112 mm (4.4 inches)	78%	very high
June Weather	22°C (72°F)	83 mm (3.3 inches)	80%	very high
July Weather	24°C (75°F)	96 mm (3.8 inches)	81%	very high
August Weather	21°C (71°F)	152 mm (6.0 inches)	81%	very high
September Weather	18°C (64°F)	113 mm (4.4 inches)	81%	high
October Weather	9°C (48°F)	98 mm (3.8 inches)	84%	moderate
November Weather	1°C (33°F)	32 mm (1.3 inches)	88%	moderate
December Weather	-5°C (23°F)	44 mm (1.7 inches)	84%	low