Winter Weather in Unalaska Alaska, United StatesDaily high temperatures are around 37°F, rarely falling below 28°F or exceeding 44°F. The lowest daily average high temperature is 35°F on January 21. Daily low temperatures are around 32°F, rarely falling below 21°F or exceeding 39°F. The lowest daily average low temperature is 30°F on January 23. 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. The figure below shows you a compact characterization of the hourly average winter 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. 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). CloudsThe winter in Unalaska experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 74% throughout the season. The highest chance of overcast or mostly cloudy conditions is 78% on January 25. The clearest day of the winter is December 1, with clear, mostly clear, or partly cloudy conditions 29% 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%. PrecipitationA 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 winter is very rapidly decreasing, starting the season at 45% and ending it at 35%. 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 winter in Unalaska, the chance of a day with only rain decreases from 39% to 27%, the chance of a day with mixed snow and rain remains an essentially constant 5% throughout, and the chance of a day with only snow increases from 2% to 4%. RainfallTo 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 winter in Unalaska is rapidly decreasing, starting the season at 3.9 inches, when it rarely exceeds 5.8 inches or falls below 1.8 inches, and ending the season at 2.2 inches, when it rarely exceeds 3.9 inches or falls below 0.6 inches. The highest average 31-day accumulation is 4.0 inches on December 8. SnowfallAs 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 winter in Unalaska is increasing, starting the season at 1.9 inches, when it rarely exceeds 6.4 inches or falls below -0.0 inches, and ending the season at 3.8 inches, when it rarely exceeds 11.7 inches. The highest average 31-day accumulation is 6.7 inches on January 27. SunOver the course of the winter in Unalaska, the length of the day is very rapidly increasing. From the start to the end of the season, the length of the day increases by 3 hours, 1 minute, implying an average daily increase of 2 minutes, 2 seconds, and weekly increase of 14 minutes, 16 seconds. The shortest day of the winter is December 20, with 7 hours, 24 minutes of daylight and the longest day is February 28, with 10 hours, 47 minutes of daylight. The latest sunrise of the winter in Unalaska is 9:24 AM on December 28 and the earliest sunrise is 1 hour, 29 minutes earlier at 7:55 AM on February 28. The earliest sunset is 4:44 PM on December 12 and the latest sunset is 1 hour, 58 minutes later at 6:42 PM on February 28. Daylight saving time is observed in Unalaska during 2024, but it neither starts nor ends during the winter, so the entire season is in daylight saving time. 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. 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. MoonThe figure below presents a compact representation of key lunar data for the winter 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. HumidityWe 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 winter, remaining around 0% throughout. WindThis 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 decreasing during the winter, decreasing from 19.9 miles per hour to 18.3 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 wind direction in Unalaska during the winter is predominantly out of the west from December 1 to December 21, the north from December 21 to February 16 and from February 22 to February 28, and the east from February 16 to February 22. Water TemperatureUnalaska 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 gradually decreasing during the winter, falling by 3°F, from 42°F to 39°F, over the course of the season. Growing SeasonDefinitions 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. The winter in Unalaska is more likely than not fully outside of the growing season, with the chance that a given day is in the growing season reaching a low of -0% on February 6. 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 gradually decreasing during the winter, decreasing by 159°F, from 159°F to 0°F, over the course of the season. Solar EnergyThis 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 increasing during the winter, rising by 1.1 kWh, from 0.5 kWh to 1.7 kWh, over the course of the season. The lowest average daily incident shortwave solar energy during the winter is 0.4 kWh on December 15. TopographyFor 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%). Data SourcesThis 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 PointThere 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 DataAll 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. DisclaimerThe 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. Please review our full terms contained on our Terms of Service page. |