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September Weather in Star Valley, United States

Last updated: June 24, 2025

In Star Valley, United States, the average temperature in September hovers around 21°C (70°F). However, you can expect a range, with minimums dropping to 4°C (39°F) and maximums soaring up to 36°C (98°F). During this month, precipitation averages 36 mm (1.4 in) spread over 4 days, making the average humidity sit at a comfortable 59%.

September Temperature in Star Valley

In September in Star Valley, the average temperature is 21°C (70°F). The maximum can reach 36°C (98°F), while the minimum can be as low as 4°C (39°F). This range makes it an ideal time for travelers to enjoy a variety of outdoor activities, from exploring the sights during the warm days to experiencing the cooler evenings.

September Weather in Star Valley: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Star Valley, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Star Valley, September typically has an average temperature of 21°C (70°F), with highs reaching up to 36°C (98°F) and lows dropping to around 4°C (39°F).
JanFebMarAprMayJunJulAugSepOctNovDec394146566375767570584941
Data source: Temperature data for Star Valley 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 Star Valley

In Star Valley in September, the precipitation amount is 36 mm (1.4 in) over the course of 4 days.

September Precipitation Trends in Star Valley

The chart displays monthly precipitation patterns in Star Valley, 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 Star Valley, September typically receives around 36 mm (1.4 inches) of precipitation spread over approximately 4 days.
JanFebMarAprMayJunJulAugSepOctNovDec648065111771115036363252
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Star Valley

In Star Valley in September humidity is 59%. With an average temperature of 21°C (70°F), this humidity feels like a pleasantly warm embrace, making it ideal for leisurely strolls and outdoor activities.

September Average Humidity in Star Valley

This chart illustrates the average monthly humidity levels in Star Valley, 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 Star Valley is approximately 59%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec80%83%72%63%46%35%33%41%59%70%79%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Star Valley

In Star Valley in September, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in Star Valley.

Maximum UV Index Levels in Star Valley for September

The chart shows the monthly maximum UV Index (UVI) for Star Valley 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 Star Valley typically reaches 11, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec479111213121111865
Data source: Star Valley 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 Star Valley Compares to Other Months

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

This table compares monthly weather conditions in Star Valley, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather4°C (40°F)64 mm (2.5 inches)80%moderate
February Weather5°C (41°F)80 mm (3.1 inches)83%high
March Weather8°C (47°F)64 mm (2.5 inches)72%very high
April Weather13°C (56°F)11 mm (0.4 inches)63%extreme
May Weather17°C (63°F)17 mm (0.7 inches)46%extreme
June Weather24°C (75°F)7 mm (0.3 inches)35%extreme
July Weather24°C (76°F)111 mm (4.4 inches)33%extreme
August Weather24°C (75°F)50 mm (1.9 inches)41%extreme
September Weather21°C (70°F)36 mm (1.4 inches)59%extreme
October Weather15°C (59°F)36 mm (1.4 inches)70%very high
November Weather10°C (50°F)32 mm (1.3 inches)79%high
December Weather5°C (41°F)51 mm (2.0 inches)82%moderate

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