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September Weather in Unalaska, United States

Last updated: June 24, 2025

In Unalaska, United States, the average temperature in September hovers around 9°C (48°F). With lows dipping to 2°C (36°F) and highs reaching 17°C (63°F), it's a month of mild weather. Expect 117 mm (4.6 in) of precipitation spread over 17 days, contributing to an average humidity of 86%. Prepare for a cozy, damp atmosphere!

September Temperature in Unalaska

In September in Unalaska, the average temperature is 9°C (48°F). Maximums can reach 17°C (63°F) and minimums can drop to as low as 2°C (36°F). This pleasant climate makes Unalaska an ideal destination for travelers seeking a mild escape during this time of year.

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

The chart illustrates September temperature patterns in Unalaska, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Unalaska, September typically has an average temperature of 9°C (48°F), with highs reaching up to 17°C (63°F) and lows dropping to around 2°C (36°F).
JanFebMarAprMayJunJulAugSepOctNovDec303332354045505147423632
Data source: Temperature data for Unalaska 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 Unalaska

In Unalaska in September, the precipitation amount is 117 mm (4.6 in) over the course of 17 days.

September Precipitation Trends in Unalaska

The chart displays monthly precipitation patterns in Unalaska, 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 Unalaska, September typically receives around 117 mm (4.6 inches) of precipitation spread over approximately 17 days.
JanFebMarAprMayJunJulAugSepOctNovDec9515792991151006589117147113157
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Unalaska

In Unalaska in September, humidity is 86%. With an average temperature of 9°C (48°F), this humidity feels like a damp chill that wraps around you, making outdoor activities uncomfortable and travel less enjoyable.

September Average Humidity in Unalaska

This chart illustrates the average monthly humidity levels in Unalaska, 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 Unalaska is approximately 86%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec83%84%83%84%90%93%95%92%86%82%81%83%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Unalaska

In Unalaska in September, the maximum UV index reaches 5, which corresponds to a moderate Exposure Category. Under these conditions, the estimated time to burn is approximately 30 minutes. For more details, you can check the Hourly UV Index in Unalaska.

Maximum UV Index Levels in Unalaska for September

The chart shows the monthly maximum UV Index (UVI) for Unalaska 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 Unalaska typically reaches 5, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec123567885321
Data source: Unalaska 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 Unalaska Compares to Other Months

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

This table compares monthly weather conditions in Unalaska, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (30°F)95 mm (3.8 inches)83%low
February Weather1°C (33°F)157 mm (6.2 inches)84%low
March Weather0°C (32°F)92 mm (3.6 inches)83%moderate
April Weather2°C (35°F)99 mm (3.9 inches)84%moderate
May Weather4°C (40°F)115 mm (4.5 inches)90%high
June Weather7°C (46°F)100 mm (3.9 inches)93%high
July Weather10°C (50°F)65 mm (2.6 inches)95%very high
August Weather11°C (51°F)89 mm (3.5 inches)92%very high
September Weather9°C (48°F)117 mm (4.6 inches)86%moderate
October Weather5°C (42°F)147 mm (5.8 inches)82%moderate
November Weather2°C (37°F)113 mm (4.5 inches)81%low
December Weather0°C (32°F)157 mm (6.2 inches)82%low

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