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September Weather in Ketchum, United States

Last updated: June 24, 2025

In September, the average temperature in Ketchum, United States hovers around 10°C (51°F). Expect temperature fluctuations with a minimum of -13°C (10°F) and a maximum of 29°C (84°F). During this month, anticipate 30 mm (1.2 in) of precipitation spread over 5 days, coupled with an average humidity of 46%.

September Temperature in Ketchum

In September in Ketchum, the average temperature is 10°C (51°F). Maximum temperatures can reach 29°C (84°F), while minimums can drop as low as -13°C (10°F). This range of temperatures suggests that travelers should be prepared for both warm days and chilly nights.

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

The chart illustrates September temperature patterns in Ketchum, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Ketchum, September typically has an average temperature of 10°C (51°F), with highs reaching up to 29°C (84°F) and lows dropping to around -13°C (10°F).
JanFebMarAprMayJunJulAugSepOctNovDec171826313952626050352616
Data source: Temperature data for Ketchum 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 Ketchum

In Ketchum in September, the precipitation amount is 30 mm (1.2 in) over the course of 5 days.

September Precipitation Trends in Ketchum

The chart displays monthly precipitation patterns in Ketchum, 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 Ketchum, September typically receives around 30 mm (1.2 inches) of precipitation spread over approximately 5 days.
JanFebMarAprMayJunJulAugSepOctNovDec568660526146153330424649
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Ketchum

In Ketchum in September, humidity is 46%. With an average temperature of 10°C (51°F), this humidity feels like a refreshing coolness that invigorates your senses while traveling, making it ideal for exploring without feeling sticky or overly warm.

September Average Humidity in Ketchum

This chart illustrates the average monthly humidity levels in Ketchum, 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 Ketchum is approximately 46%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec91%92%85%76%66%62%53%42%46%64%83%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Ketchum

In Ketchum in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Ketchum.

Maximum UV Index Levels in Ketchum for September

The chart shows the monthly maximum UV Index (UVI) for Ketchum 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 Ketchum typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3589111211109643
Data source: Ketchum 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 Ketchum Compares to Other Months

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

This table compares monthly weather conditions in Ketchum, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-8°C (17°F)56 mm (2.2 inches)91%moderate
February Weather-8°C (18°F)86 mm (3.4 inches)92%moderate
March Weather-3°C (26°F)60 mm (2.4 inches)85%very high
April Weather0°C (31°F)52 mm (2.0 inches)76%very high
May Weather4°C (40°F)61 mm (2.4 inches)66%extreme
June Weather11°C (52°F)46 mm (1.8 inches)62%extreme
July Weather16°C (62°F)15 mm (0.6 inches)53%extreme
August Weather15°C (60°F)33 mm (1.3 inches)42%very high
September Weather10°C (51°F)30 mm (1.2 inches)46%very high
October Weather2°C (35°F)42 mm (1.6 inches)64%high
November Weather-4°C (26°F)46 mm (1.8 inches)83%moderate
December Weather-9°C (16°F)49 mm (1.9 inches)87%moderate

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