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September Weather in Bismarck, United States

Last updated: June 24, 2025

In September, the average temperature in Bismarck, United States is a pleasant 21°C (70°F). Expect a range between a cool 6°C (42°F) and a warm 34°C (93°F). Rainfall can be expected too, with an average precipitation of 71 mm (2.8 in) spread over 7 days. The average humidity hovers around a notable 80%, making it a month full of varied weather experiences.

September Temperature in Bismarck

In September in Bismarck, the average temperature is 21°C (70°F), with maximums reaching 34°C (93°F) and minimums dropping as low as 6°C (42°F). This pleasant climate makes Bismarck an ideal destination for travelers seeking a comfortable getaway.

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

The chart illustrates September temperature patterns in Bismarck, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Bismarck, September typically has an average temperature of 21°C (70°F), with highs reaching up to 34°C (93°F) and lows dropping to around 6°C (42°F).
JanFebMarAprMayJunJulAugSepOctNovDec293142526474777470574135
Data source: Temperature data for Bismarck 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 Bismarck

In Bismarck in September, the precipitation amount is 71 mm (2.8 in) over a span of 7 days.

September Precipitation Trends in Bismarck

The chart displays monthly precipitation patterns in Bismarck, 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 Bismarck, September typically receives around 71 mm (2.8 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec777811011015110588111711217760
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Bismarck

In Bismarck in September humidity is 80%. With an average temperature of 21°C (70°F), this humidity feels like a warm, enveloping blanket that can make even short walks feel draining, urging travelers to seek shade or a cool drink frequently.

September Average Humidity in Bismarck

This chart illustrates the average monthly humidity levels in Bismarck, 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 Bismarck is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%83%84%85%79%82%80%81%80%82%88%84%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Bismarck

In Bismarck 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 Bismarck.

Maximum UV Index Levels in Bismarck for September

The chart shows the monthly maximum UV Index (UVI) for Bismarck 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 Bismarck typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910111098642
Data source: Bismarck 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 Bismarck Compares to Other Months

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

This table compares monthly weather conditions in Bismarck, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (29°F)77 mm (3.0 inches)82%moderate
February Weather0°C (31°F)78 mm (3.1 inches)83%moderate
March Weather6°C (42°F)110 mm (4.3 inches)84%high
April Weather11°C (52°F)110 mm (4.3 inches)85%very high
May Weather18°C (65°F)151 mm (6.0 inches)79%very high
June Weather23°C (74°F)105 mm (4.1 inches)82%extreme
July Weather25°C (77°F)88 mm (3.5 inches)80%very high
August Weather24°C (75°F)111 mm (4.4 inches)81%very high
September Weather21°C (70°F)71 mm (2.8 inches)80%very high
October Weather14°C (57°F)121 mm (4.7 inches)82%high
November Weather5°C (41°F)77 mm (3.0 inches)88%moderate
December Weather2°C (36°F)60 mm (2.4 inches)84%low

Compare Bismarck's Climate with Cities Worldwide