September Weather in Groton, United States

Last updated: June 24, 2025

In September, the average temperature in Groton, United States hovers around 17°C (63°F), providing a comfortable climate for all. Expect a minimum chill of 2°C (36°F) and a warm maximum of 34°C (93°F). During this month, precipitation totals 88 mm (3.5 in), typically spread over 8 days, contributing to an average humidity of 77%. Prepare for a mix of sunny days and refreshing showers!

September Temperature in Groton

In September in Groton, the average temperature is 17°C (63°F), with maximums reaching 34°C (93°F) and minimums as low as 2°C (36°F). This wide temperature range makes Groton an exciting destination for travelers seeking both warmth and cooler escapes.

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

The chart illustrates September temperature patterns in Groton, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Groton, September typically has an average temperature of 17°C (63°F), with highs reaching up to 34°C (93°F) and lows dropping to around 2°C (36°F).

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

September Precipitation in Groton

In Groton in September, the precipitation amount is 88 mm (3.5 in) over the course of 8 days.

September Precipitation Trends in Groton

The chart displays monthly precipitation patterns in Groton, 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 Groton, September typically receives around 88 mm (3.5 inches) of precipitation spread over approximately 8 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

September Humidity in Groton

In Groton in September, humidity is 77%. With an average temperature of 17°C (63°F), this humidity feels like a cozy blanket wrapped around you, creating a muggy atmosphere that can be a bit uncomfortable for traveling, making you want to seek shade and hydration as you explore.

September Average Humidity in Groton

This chart illustrates the average monthly humidity levels in Groton, 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 Groton is approximately 77%, 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 Groton

In Groton 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 Groton.

Maximum UV Index Levels in Groton for September

The chart shows the monthly maximum UV Index (UVI) for Groton 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 Groton typically reaches 7, which falls under the high exposure category.

Data source: Groton 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 Groton Compares to Other Months

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

This table compares monthly weather conditions in Groton, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-10°C (15°F)	18 mm (0.7 inches)	81%	moderate
February Weather	-10°C (14°F)	16 mm (0.6 inches)	85%	moderate
March Weather	-1°C (31°F)	35 mm (1.4 inches)	76%	moderate
April Weather	5°C (41°F)	47 mm (1.9 inches)	79%	high
May Weather	14°C (57°F)	64 mm (2.5 inches)	76%	very high
June Weather	22°C (71°F)	65 mm (2.6 inches)	81%	very high
July Weather	24°C (75°F)	76 mm (3.0 inches)	82%	very high
August Weather	21°C (71°F)	108 mm (4.2 inches)	82%	very high
September Weather	17°C (63°F)	88 mm (3.5 inches)	77%	high
October Weather	8°C (46°F)	76 mm (3.0 inches)	76%	moderate
November Weather	0°C (33°F)	17 mm (0.7 inches)	84%	moderate
December Weather	-5°C (23°F)	33 mm (1.3 inches)	81%	low