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September Weather in Sioux City, United States

Last updated: June 24, 2025

In September, the average temperature in Sioux City, United States is a comfortable 20°C (68°F). However, you can expect temperatures to range from a chilly 4°C (40°F) to a warm 34°C (94°F). Prepare for some moisture too, as the region receives about 101 mm (4.0 in) of precipitation over 9 days. With an average humidity of 75%, be ready for a pleasantly humid climate!

September Temperature in Sioux City

In September in Sioux City, the average temperature is 20°C (68°F). Maximum temperatures can reach 34°C (94°F), while minimums can drop to as low as 4°C (40°F). This diverse temperature range makes Sioux City an ideal destination for travelers who enjoy a mix of warm and cool weather experiences.

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

The chart illustrates September temperature patterns in Sioux City, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Sioux City, September typically has an average temperature of 20°C (68°F), with highs reaching up to 34°C (94°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec232238476174777368513729
Data source: Temperature data for Sioux City 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 Sioux City

In Sioux City in September, the total precipitation amount is 101 mm (4.0 in), occurring over a span of 9 days.

September Precipitation Trends in Sioux City

The chart displays monthly precipitation patterns in Sioux City, 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 City, September typically receives around 101 mm (4.0 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec2829818014010267109101772741
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Sioux City

In Sioux City in September, humidity is 75%. With an average temperature of 20°C (68°F), this humidity feels like a warm, muggy embrace that can leave travelers feeling sticky and exhausted.

September Average Humidity in Sioux City

This chart illustrates the average monthly humidity levels in Sioux City, 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 City is approximately 75%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec80%84%75%79%74%81%82%80%75%77%85%83%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Sioux City

In Sioux City 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 City.

Maximum UV Index Levels in Sioux City for September

The chart shows the monthly maximum UV Index (UVI) for Sioux City 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 City typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35589111098532
Data source: Sioux City 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 City Compares to Other Months

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

This table compares monthly weather conditions in Sioux City, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (23°F)28 mm (1.1 inches)80%moderate
February Weather-5°C (23°F)29 mm (1.2 inches)84%moderate
March Weather3°C (38°F)81 mm (3.2 inches)75%moderate
April Weather9°C (48°F)80 mm (3.2 inches)79%very high
May Weather16°C (61°F)140 mm (5.5 inches)74%very high
June Weather23°C (74°F)102 mm (4.0 inches)81%extreme
July Weather25°C (77°F)66 mm (2.6 inches)82%very high
August Weather23°C (73°F)109 mm (4.3 inches)80%very high
September Weather20°C (68°F)101 mm (4.0 inches)75%very high
October Weather10°C (51°F)77 mm (3.0 inches)77%moderate
November Weather3°C (38°F)27 mm (1.0 inches)85%moderate
December Weather-2°C (29°F)41 mm (1.6 inches)83%low

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