Average Weather in April in Unalaska Alaska, United States
Daily high temperatures increase by 3°F, from 38°F to 41°F, rarely falling below 31°F or exceeding 46°F.
Daily low temperatures increase by 3°F, from 32°F to 35°F, rarely falling below 25°F or exceeding 39°F.
For reference, on August 14, 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 April
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on April. 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 April
The month of April in Unalaska experiences gradually decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 70% to 65%.
The clearest day of the month is April 30, with clear, mostly clear, or partly cloudy conditions 34% of the time.
For reference, on July 17, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 82%, while on October 14, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 41%.
Cloud Cover Categories in April
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 April is rapidly decreasing, starting the month at 34% and ending it at 26%.
For reference, the year's highest daily chance of a wet day is 47% on December 17, and its lowest chance is 25% on May 5.
Over the course of April in Unalaska, the chance of a day with only rain decreases from 28% to 25%, the chance of a day with mixed snow and rain decreases from 4% to 1%, and the chance of a day with only snow remains an essentially constant 1% throughout.
Probability of Precipitation in April
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during April in Unalaska is gradually decreasing, starting the month at 2.1 inches, when it rarely exceeds 3.4 inches or falls below 0.9 inches, and ending the month at 1.8 inches, when it rarely exceeds 2.9 inches or falls below 0.8 inches.
The lowest average 31-day accumulation is 1.7 inches on April 25.
Average Monthly Rainfall in April
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. As with rainfall, we consider the liquid-equivalent snowfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day liquid-equivalent snowfall during April in Unalaska is essentially constant, remaining about 0.1 inches throughout, and rarely exceeding 0.5 inches or falling below -0.0 inches.
Average Monthly Liquid-Equivalent Snowfall in April
Over the course of April in Unalaska, the length of the day is very rapidly increasing. From the start to the end of the month, the length of the day increases by 2 hours, 0 minutes, implying an average daily increase of 4 minutes, 9 seconds, and weekly increase of 29 minutes, 2 seconds.
The shortest day of the month is April 1, with 13 hours, 4 minutes of daylight and the longest day is April 30, with 15 hours, 5 minutes of daylight.
Hours of Daylight and Twilight in April
The latest sunrise of the month in Unalaska is 7:38 AM on April 1 and the earliest sunrise is 1 hour, 7 minutes earlier at 6:31 AM on April 30.
The earliest sunset is 8:42 PM on April 1 and the latest sunset is 54 minutes later at 9:36 PM on April 30.
Daylight saving time is observed in Unalaska during 2018, but it neither starts nor ends during April, so the entire month is in daylight saving time.
For reference, on June 21, 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 April
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 April, remaining around 0% throughout.
Humidity Comfort Levels in April
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 rapidly decreasing during April, decreasing from 18.2 miles per hour to 16.0 miles per hour over the course of the month.
For reference, on November 25, the windiest day of the year, the daily average wind speed is 20.2 miles per hour, while on July 18, the calmest day of the year, the daily average wind speed is 11.2 miles per hour.
Average Wind Speed in April
Wind Direction in April
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 essentially constant during April, remaining around 39°F throughout.
Average Water Temperature in April
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 29 to around November 10, rarely starting before April 8 or after May 20, and rarely ending before October 16 or after December 9.
During April in Unalaska, the chance that a given day is within the growing season is rapidly increasing rising from 5% to 53% over the course of the month.
Time Spent in Various Temperature Bands and the Growing Season in April
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 April, remaining around 0°F throughout.
Growing Degree Days in April
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 increasing during April, rising by 1.3 kWh, from 2.9 kWh to 4.1 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in April
For the purposes of this report, the geographical coordinates of Unalaska are 53.874 deg latitude, -166.537 deg longitude, and 177 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 year round, 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.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.
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.