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September Weather in Boulder City, United States

Last updated: June 24, 2025

In September, the average temperature in Boulder City, United States hovers around 30°C (86°F), with a minimum of 13°C (55°F) and a scorching maximum reaching up to 45°C (114°F). Expect minimal precipitation of just 5 mm (0.2 in) over the course of 1 day, complemented by an average humidity of 48%. Perfect for those seeking sunny days!

September Temperature in Boulder City

In September in Boulder City, the average temperature is 30°C (86°F), with maximums reaching 45°C (114°F) and minimums dropping as low as 13°C (55°F). Travelers should be prepared for hot days and cooler nights, making it essential to pack accordingly.

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

The chart illustrates September temperature patterns in Boulder City, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Boulder City, September typically has an average temperature of 30°C (86°F), with highs reaching up to 45°C (114°F) and lows dropping to around 13°C (55°F).
JanFebMarAprMayJunJulAugSepOctNovDec495361717891959486706049
Data source: Temperature data for Boulder 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 Boulder City

In Boulder City in September, the precipitation amount is 5 mm (0.2 in) over a duration of 1 day.

September Precipitation Trends in Boulder City

The chart displays monthly precipitation patterns in Boulder 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 Boulder City, September typically receives around 5 mm (0.2 inches) of precipitation spread over approximately 1 days.
JanFebMarAprMayJunJulAugSepOctNovDec2122205611811581916
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Boulder City

In Boulder City in September, humidity is 48%. With an average temperature of 30°C (86°F), this humidity feels like a warm embrace, making travel enjoyable yet slightly heavy, prompting visitors to seek refreshing breaks in shaded areas or cool indoor spaces.

September Average Humidity in Boulder City

This chart illustrates the average monthly humidity levels in Boulder 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 Boulder City is approximately 48%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec77%80%68%58%45%31%27%30%48%60%70%77%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Boulder City

In Boulder City in September, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Boulder City.

Maximum UV Index Levels in Boulder City for September

The chart shows the monthly maximum UV Index (UVI) for Boulder 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 Boulder City typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec468101112121110753
Data source: Boulder 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 Boulder City Compares to Other Months

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

This table compares monthly weather conditions in Boulder City, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather10°C (50°F)21 mm (0.8 inches)77%moderate
February Weather12°C (53°F)21 mm (0.8 inches)80%high
March Weather16°C (61°F)20 mm (0.8 inches)68%very high
April Weather22°C (71°F)5 mm (0.2 inches)58%very high
May Weather26°C (78°F)6 mm (0.2 inches)45%extreme
June Weather33°C (91°F)1 mm (0.0 inches)31%extreme
July Weather35°C (96°F)17 mm (0.7 inches)27%extreme
August Weather35°C (95°F)11 mm (0.4 inches)30%extreme
September Weather30°C (86°F)5 mm (0.2 inches)48%very high
October Weather21°C (71°F)8 mm (0.3 inches)59%high
November Weather15°C (60°F)19 mm (0.7 inches)70%moderate
December Weather10°C (50°F)15 mm (0.6 inches)77%moderate

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