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Fall Weather in Unalaska Alaska, United States

Daily high temperatures decrease by 16°F, from 55°F to 39°F, rarely falling below 33°F or exceeding 61°F.

Daily low temperatures decrease by 14°F, from 48°F to 34°F, rarely falling below 28°F or exceeding 52°F.

For reference, on August 13, the hottest day of the year, temperatures in Unalaska typically range from 49°F to 56°F, while on January 23, the coldest day of the year, they range from 30°F to 36°F.

Average High and Low Temperature in the Fall in Unalaska

Average High and Low Temperature in the Fall in UnalaskaSepOctNov20°F20°F25°F25°F30°F30°F35°F35°F40°F40°F45°F45°F50°F50°F55°F55°F60°F60°F65°F65°FSummerWinterSep 155°FSep 155°F48°F48°FNov 3039°FNov 3039°F34°F34°FOct 149°FOct 149°F43°F43°FNov 143°FNov 143°F37°F37°F
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average fall temperatures. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in the Fall in Unalaska

Average Hourly Temperature in the Fall in UnalaskaSepOctNov12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMSummerWintervery coldcold
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Ólafsvík, Iceland (4,002 miles away) and Evjen, Norway (4,002 miles) are the far-away foreign places with temperatures most similar to Unalaska (view comparison).

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The fall in Unalaska experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 65% throughout the season. The lowest chance of overcast or mostly cloudy conditions is 59% on October 13.

The clearest day of the fall is October 13, with clear, mostly clear, or partly cloudy conditions 41% of the time.

For reference, on July 16, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 82%, while on October 13, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 41%.

Cloud Cover Categories in the Fall in Unalaska

Cloud Cover Categories in the Fall in UnalaskaSepOctNov0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%SummerWinterJul 1618%Jul 1618%Sep 130%Sep 130%Nov 3029%Nov 3029%Oct 139%Oct 139%Nov 139%Nov 139%clearmostly clearpartly cloudymostly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Unalaska, the chance of a wet day over the course of the fall is rapidly increasing, starting the season at 37% and ending it at 44%.

For reference, the year's highest daily chance of a wet day is 47% on December 16, and its lowest chance is 25% on May 4.

Over the course of the fall in Unalaska, the chance of a day with only rain increases from 37% to 39%, the chance of a day with mixed snow and rain increases from 0% to 3%, and the chance of a day with only snow remains an essentially constant 1% throughout.

Probability of Precipitation in the Fall in Unalaska

Probability of Precipitation in the Fall in UnalaskaSepOctNov0%0%5%5%10%10%15%15%20%20%25%25%30%30%35%35%40%40%45%45%50%50%SummerWinterSep 137%Sep 137%Nov 3044%Nov 3044%Oct 139%Oct 139%Nov 143%Nov 143%mixedrainsnow
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the fall in Unalaska is increasing, starting the season at 3.1 inches, when it rarely exceeds 4.7 inches or falls below 1.5 inches, and ending the season at 3.9 inches, when it rarely exceeds 5.8 inches or falls below 1.7 inches.

Average Monthly Rainfall in the Fall in Unalaska

Average Monthly Rainfall in the Fall in UnalaskaSepOctNov0 in0 in1 in1 in2 in2 in3 in3 in4 in4 in5 in5 in6 in6 in7 in7 inSummerWinterSep 13.1 inSep 13.1 inNov 303.9 inNov 303.9 inOct 13.7 inOct 13.7 inNov 13.8 inNov 13.8 in
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day snowfall during the fall in Unalaska is increasing, starting the season at -0.0 inches, when it rarely exceeds 0.0 inches or falls below -0.0 inches, and ending the season at 1.8 inches, when it rarely exceeds 6.1 inches or falls below -0.0 inches.

Average Monthly Snowfall in the Fall in Unalaska

Average Monthly Snowfall in the Fall in UnalaskaSepOctNov0 in0 in2 in2 in4 in4 in6 in6 in8 in8 in10 in10 in12 in12 in14 in14 inSummerWinterSep 1-0.0 inSep 1-0.0 inNov 301.8 inNov 301.8 inOct 1-0.0 inOct 1-0.0 inNov 10.2 inNov 10.2 in
The average snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.

Over the course of the fall in Unalaska, the length of the day is very rapidly decreasing. From the start to the end of the season, the length of the day decreases by 5 hours, 50 minutes, implying an average daily decrease of 3 minutes, 53 seconds, and weekly decrease of 27 minutes, 14 seconds.

The shortest day of the fall is November 30, with 7 hours, 48 minutes of daylight and the longest day is September 1, with 13 hours, 38 minutes of daylight.

Hours of Daylight and Twilight in the Fall in Unalaska

Hours of Daylight and Twilight in the Fall in UnalaskaSepOctNov0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrSummerWinterSep 2212 hr, 14 minSep 2212 hr, 14 minnightnightdaydayNov 307 hr, 48 minNov 307 hr, 48 minNov 19 hr, 22 minNov 19 hr, 22 min
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the fall in Unalaska is 7:16 AM on September 1 and the latest sunrise is 1 hour, 54 minutes later at 9:10 AM on November 2.

The latest sunset is 8:54 PM on September 1 and the earliest sunset is 4 hours, 5 minutes earlier at 4:49 PM on November 30.

Daylight saving time (DST) starts at 1:00 AM on November 3, 2024, shifting sunrise and sunset to be an hour later.

For reference, on June 20, the longest day of the year, the Sun rises at 5:34 AM and sets 17 hours, 7 minutes later, at 10:41 PM, while on December 21, the shortest day of the year, it rises at 9:22 AM and sets 7 hours, 24 minutes later, at 4:46 PM.

Sunrise & Sunset with Twilight and Daylight Saving Time in the Fall in Unalaska

Sunrise & Sunset with Twilight and Daylight Saving Time in the Fall in UnalaskaSepOctNov2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AM2 AMSummerWinter7:16 AM7:16 AMSep 18:54 PMSep 18:54 PM9:00 AM9:00 AMNov 304:49 PMNov 304:49 PM9:10 AM9:10 AMNov 26:28 PMNov 26:28 PM8:09 AM8:09 AMOct 17:40 PMOct 17:40 PMDSTNov 3DSTNov 3SolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day in the fall. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

Solar Elevation and Azimuth in the Fall in Unalaska

Solar Elevation and Azimuth in the Fall in UnalaskaSepOctNov12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMSummerWinter01020300010203040
northeastsouthwest
Solar elevation and azimuth in the the fall of 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for the fall of 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

Moon Rise, Set & Phases in the Fall in Unalaska

Moon Rise, Set & Phases in the Fall in UnalaskaSepOctNov12 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMSummerWinterAug 42:14 AMAug 42:14 AMAug 199:26 AMAug 199:26 AMSep 24:56 PMSep 24:56 PMSep 175:35 PMSep 175:35 PMOct 29:50 AMOct 29:50 AMOct 172:27 AMOct 172:27 AMNov 13:48 AMNov 13:48 AMNov 1511:29 AMNov 1511:29 AMNov 308:22 PMNov 308:22 PMDec 1411:02 PMDec 1411:02 PMDec 3012:28 PMDec 3012:28 PM10:22 PM10:22 PM6:33 AM6:33 AM6:45 AM6:45 AM9:03 PM9:03 PM8:17 PM8:17 PM8:43 AM8:43 AM8:13 AM8:13 AM7:33 PM7:33 PM6:43 PM6:43 PM9:17 AM9:17 AM9:45 AM9:45 AM6:11 PM6:11 PM8:54 AM8:54 AM3:55 PM3:55 PM10:13 AM10:13 AM4:14 PM4:14 PM
The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Unalaska is essentially constant during the fall, remaining around 0% throughout.

Humidity Comfort Levels in the Fall in Unalaska

Humidity Comfort Levels in the Fall in UnalaskaSepOctNov0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%SummerWinterOct 160%Oct 160%Sep 10%Sep 10%Nov 300%Nov 300%Oct 10%Oct 10%Nov 10%Nov 10%drydrycomfortablecomfortable
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Unalaska is very rapidly increasing during the fall, increasing from 14.1 miles per hour to 19.8 miles per hour over the course of the season.

For reference, on November 24, the windiest day of the year, the daily average wind speed is 20.2 miles per hour, while on July 17, the calmest day of the year, the daily average wind speed is 11.2 miles per hour.

The highest daily average wind speed during the fall is 20.2 miles per hour on November 24.

Average Wind Speed in the Fall in Unalaska

Average Wind Speed in the Fall in UnalaskaSepOctNov0 mph0 mph5 mph5 mph10 mph10 mph15 mph15 mph20 mph20 mph25 mph25 mph30 mph30 mphSummerWinterNov 2420.2 mphNov 2420.2 mphSep 114.1 mphSep 114.1 mphOct 117.7 mphOct 117.7 mphNov 119.4 mphNov 119.4 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The hourly average wind direction in Unalaska throughout the fall is predominantly from the west, with a peak proportion of 44% on September 2.

Wind Direction in the Fall in Unalaska

Wind Direction in the Fall in UnalaskaWNSepOctNov0%100%20%80%40%60%60%40%80%20%100%0%SummerWinterwestsoutheastnorth
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Unalaska is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature in Unalaska is decreasing during the fall, falling by 6°F, from 49°F to 42°F, over the course of the season.

Average Water Temperature in the Fall in Unalaska

Average Water Temperature in the Fall in UnalaskaSepOctNov38°F38°F40°F40°F42°F42°F44°F44°F46°F46°F48°F48°F50°F50°F52°F52°FSummerWinterSep 149°FSep 149°FNov 3042°FNov 3042°FOct 146°FOct 146°FNov 144°FNov 144°F
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Unalaska typically lasts for 6.4 months (195 days), from around April 28 to around November 9, rarely starting before April 7 or after May 19, and rarely ending before October 15 or after December 8.

During the fall in Unalaska, the chance that a given day is within the growing season is very rapidly decreasing falling from 100% to 15% over the course of the season.

Time Spent in Various Temperature Bands and the Growing Season in the Fall in Unalaska

Time Spent in Various Temperature Bands and the Growing Season in the Fall in Unalaskagrowing seasonSepOctNov0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%SummerWinter100%Sep 1100%Sep 1Nov 3015%Nov 3015%98%Oct 198%Oct 167%Nov 167%Nov 1Sep 8100%Sep 8100%freezingvery coldcoldcool
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Unalaska are essentially constant during the fall, remaining within 15°F of 144°F throughout.

Growing Degree Days in the Fall in Unalaska

Growing Degree Days in the Fall in UnalaskaSepOctNov60°F60°F80°F80°F100°F100°F120°F120°F140°F140°F160°F160°F180°F180°F200°F200°F220°F220°F240°F240°FSummerWinterSep 1129°FSep 1129°FNov 30159°FNov 30159°FOct 1156°FOct 1156°FNov 1159°FNov 1159°F
The average growing degree days accumulated over the course of the fall, with 25th to 75th and 10th to 90th percentile bands.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Unalaska is very rapidly decreasing during the fall, falling by 2.7 kWh, from 3.2 kWh to 0.5 kWh, over the course of the season.

Average Daily Incident Shortwave Solar Energy in the Fall in Unalaska

Average Daily Incident Shortwave Solar Energy in the Fall in UnalaskaSepOctNov0.0 kWh0.0 kWh0.5 kWh0.5 kWh1.0 kWh1.0 kWh1.5 kWh1.5 kWh2.0 kWh2.0 kWh2.5 kWh2.5 kWh3.0 kWh3.0 kWh3.5 kWh3.5 kWh4.0 kWh4.0 kWh4.5 kWh4.5 kWh5.0 kWh5.0 kWh5.5 kWh5.5 kWh6.0 kWh6.0 kWhSummerWinterSep 13.2 kWhSep 13.2 kWhNov 300.5 kWhNov 300.5 kWhOct 12.2 kWhOct 12.2 kWhNov 11.1 kWhNov 11.1 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

For the purposes of this report, the geographical coordinates of Unalaska are 53.874 deg latitude, -166.537 deg longitude, and 26 ft elevation.

The topography within 2 miles of Unalaska contains very significant variations in elevation, with a maximum elevation change of 1,850 feet and an average elevation above sea level of 255 feet. Within 10 miles contains very significant variations in elevation (3,547 feet). Within 50 miles also contains extreme variations in elevation (5,971 feet).

The area within 2 miles of Unalaska is covered by water (55%), grassland (19%), and shrubs (14%), within 10 miles by water (41%) and shrubs (24%), and within 50 miles by water (86%).

This report illustrates the typical weather in Unalaska, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There is only a single weather station, Unalaska Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of Unalaska.

At a distance of 2 kilometers from Unalaska, closer than our threshold of 150 kilometers, this station is deemed sufficiently nearby to be relied upon as our primary source for temperature and dew point records.

The station records are corrected for the elevation difference between the station and Unalaska according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.

Please note that the station records themselves may additionally have been back-filled using other nearby stations or the MERRA-2 reanalysis.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for airports and weather stations are provided by AskGeo.com .

Maps are © OpenStreetMap contributors.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.

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