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September Weather in Juneau, United States

Last updated: June 24, 2025

In September, the average temperature in Juneau, United States is a pleasant 18°C (64°F). Expect a temperature range that can dip as low as 1°C (35°F) and rise up to a warm 33°C (91°F). With an average humidity of 79%, the atmosphere can feel a bit sticky. Be prepared for some rain, as 93 mm (3.6 in) of precipitation may fall over 9 days.

September Temperature in Juneau

In September in Juneau, the average temperature is 18°C (64°F). Maximums can reach 33°C (91°F), and minimums can be as low as 1°C (35°F). Travelers should be prepared for a range of temperatures and pack accordingly for both warm days and cooler evenings.

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

The chart illustrates September temperature patterns in Juneau, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Juneau, September typically has an average temperature of 18°C (64°F), with highs reaching up to 33°C (91°F) and lows dropping to around 1°C (35°F).
JanFebMarAprMayJunJulAugSepOctNovDec202134455869737064513628
Data source: Temperature data for Juneau 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 Juneau

In Juneau in September, the precipitation amount is 93 mm (3.6 in) during a span of 9 days.

September Precipitation Trends in Juneau

The chart displays monthly precipitation patterns in Juneau, 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 Juneau, September typically receives around 93 mm (3.6 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec48505810412011010397931124546
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Juneau

In Juneau in September, humidity is 79%. With an average temperature of 18°C (64°F), this humidity feels like a warm, sticky embrace that can make outdoor activities more challenging but also creates a lush, vibrant atmosphere that's perfect for exploring local culture and scenery.

September Average Humidity in Juneau

This chart illustrates the average monthly humidity levels in Juneau, 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 Juneau is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%85%85%85%78%80%78%76%79%83%88%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Juneau

In Juneau in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Juneau.

Maximum UV Index Levels in Juneau for September

The chart shows the monthly maximum UV Index (UVI) for Juneau 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 Juneau typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34589101097532
Data source: Juneau 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 Juneau Compares to Other Months

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

This table compares monthly weather conditions in Juneau, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (21°F)48 mm (1.9 inches)85%moderate
February Weather-6°C (22°F)50 mm (2.0 inches)85%moderate
March Weather1°C (35°F)58 mm (2.3 inches)85%moderate
April Weather7°C (45°F)104 mm (4.1 inches)85%very high
May Weather15°C (59°F)120 mm (4.7 inches)78%very high
June Weather21°C (69°F)110 mm (4.3 inches)80%very high
July Weather23°C (74°F)102 mm (4.0 inches)78%very high
August Weather21°C (71°F)97 mm (3.8 inches)76%very high
September Weather18°C (64°F)93 mm (3.6 inches)79%high
October Weather10°C (51°F)112 mm (4.4 inches)83%moderate
November Weather2°C (36°F)45 mm (1.8 inches)88%moderate
December Weather-2°C (29°F)46 mm (1.8 inches)81%low

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