September Weather in Sioux Falls, United States

Last updated: June 24, 2025

In September, the average temperature in Sioux Falls, United States is a pleasant 18°C (65°F). However, temperatures can vary significantly, with minimums dipping to 3°C (38°F) and soaring to a maximum of 33°C (91°F). Expect 107 mm (4.2 in) of precipitation spread over approximately 9 days, contributing to an average humidity level of 75%.

September Temperature in Sioux Falls

In September in Sioux Falls, the average temperature is 18°C (65°F). Maximum temperatures can reach 33°C (91°F), while minimums can drop as low as 3°C (38°F). This climate makes Sioux Falls a great destination for travelers seeking a mix of warm days and cool evenings.

September Weather in Sioux Falls: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Sioux Falls, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Sioux Falls, September typically has an average temperature of 18°C (65°F), with highs reaching up to 33°C (91°F) and lows dropping to around 3°C (38°F).

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

September Precipitation in Sioux Falls

In Sioux Falls in September, the precipitation amount is 107 mm (4.2 in), occurring over a span of 9 days.

September Precipitation Trends in Sioux Falls

The chart displays monthly precipitation patterns in Sioux Falls, 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 Sioux Falls, September typically receives around 107 mm (4.2 inches) of precipitation spread over approximately 9 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 Sioux Falls

In Sioux Falls in September, humidity is 75%. With an average temperature of 18°C (65°F), this humidity feels like a warm, enveloping blanket that can make outdoor exploration feel a bit stifling, potentially leading to discomfort during travel activities.

September Average Humidity in Sioux Falls

This chart illustrates the average monthly humidity levels in Sioux Falls, 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 Sioux Falls is approximately 75%, 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 Sioux Falls

In Sioux Falls 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 Sioux Falls.

Maximum UV Index Levels in Sioux Falls for September

The chart shows the monthly maximum UV Index (UVI) for Sioux Falls 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 Sioux Falls typically reaches 8, which falls under the very high exposure category.

Data source: Sioux Falls 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 Sioux Falls Compares to Other Months

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

This table compares monthly weather conditions in Sioux Falls, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-7°C (20°F)	21 mm (0.8 inches)	80%	low
February Weather	-7°C (20°F)	24 mm (0.9 inches)	84%	moderate
March Weather	2°C (35°F)	65 mm (2.6 inches)	75%	moderate
April Weather	7°C (45°F)	82 mm (3.2 inches)	79%	very high
May Weather	15°C (59°F)	128 mm (5.0 inches)	74%	very high
June Weather	23°C (73°F)	85 mm (3.3 inches)	81%	extreme
July Weather	24°C (75°F)	77 mm (3.0 inches)	82%	very high
August Weather	22°C (72°F)	94 mm (3.7 inches)	80%	very high
September Weather	18°C (65°F)	107 mm (4.2 inches)	75%	very high
October Weather	9°C (48°F)	79 mm (3.1 inches)	77%	moderate
November Weather	1°C (35°F)	25 mm (1.0 inches)	85%	moderate
December Weather	-3°C (26°F)	39 mm (1.5 inches)	83%	low