April Weather at Eielson Air Force Base United StatesDaily high temperatures increase by 19°F, from 36°F to 54°F, rarely falling below 20°F or exceeding 65°F. Daily low temperatures increase by 20°F, from 11°F to 32°F, rarely falling below -7°F or exceeding 39°F. For reference, on July 3, the hottest day of the year, temperatures at Eielson Air Force Base typically range from 52°F to 73°F, while on January 18, the coldest day of the year, they range from -14°F to 2°F. 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. Kotik, Russia (3,459 miles away); Зуунмод, Mongolia (3,727 miles); and Mogzon, Russia (3,372 miles) are the far-away foreign places with temperatures most similar to Eielson Air Force Base (view comparison). CloudsThe month of April at Eielson Air Force Base experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 59% throughout the month. The highest chance of overcast or mostly cloudy conditions is 61% on April 8. The clearest day of the month is April 30, with clear, mostly clear, or partly cloudy conditions 42% of the time. For reference, on September 25, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 65%, while on March 15, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 46%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Eielson Air Force Base, the chance of a wet day over the course of April is gradually increasing, starting the month at 6% and ending it at 9%. For reference, the year's highest daily chance of a wet day is 33% on July 11, and its lowest chance is 5% on March 21. Over the course of April at Eielson Air Force Base, the chance of a day with only rain increases from 1% to 7%, the chance of a day with mixed snow and rain remains an essentially constant 1% throughout, and the chance of a day with only snow decreases from 4% to 1%. RainfallTo 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 at Eielson Air Force Base is gradually increasing, starting the month at 0.1 inches, when it rarely exceeds 0.3 inches, and ending the month at 0.4 inches, when it rarely exceeds 1.1 inches. 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 April at Eielson Air Force Base is gradually decreasing, starting the month at 1.6 inches, when it rarely exceeds 3.8 inches or falls below -0.0 inches, and ending the month at 0.7 inches, when it rarely exceeds 2.7 inches or falls below -0.0 inches. SunOver the course of April at Eielson Air Force Base, 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 3 hours, 18 minutes, implying an average daily increase of 6 minutes, 49 seconds, and weekly increase of 47 minutes, 43 seconds. The shortest day of the month is April 1, with 13 hours, 41 minutes of daylight and the longest day is April 30, with 16 hours, 59 minutes of daylight. The latest sunrise of the month at Eielson Air Force Base is 7:02 AM on April 1 and the earliest sunrise is 1 hour, 45 minutes earlier at 5:17 AM on April 30. The earliest sunset is 8:43 PM on April 1 and the latest sunset is 1 hour, 33 minutes later at 10:16 PM on April 30. Daylight saving time is observed at Eielson Air Force Base during 2024, but it neither starts nor ends during April, so the entire month is in standard time. For reference, on June 20, the longest day of the year, the Sun rises at 3:00 AM and sets 21 hours, 39 minutes later, at 12:39 AM, while on December 21, the shortest day of the year, it rises at 10:52 AM and sets 3 hours, 48 minutes later, at 2:41 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 April 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 at Eielson Air Force Base is essentially constant during April, remaining around 0% throughout. For reference, on July 7, the muggiest day of the year, there are muggy conditions 0% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time. 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 at Eielson Air Force Base is gradually decreasing during April, decreasing from 5.6 miles per hour to 5.0 miles per hour over the course of the month. For reference, on January 8, the windiest day of the year, the daily average wind speed is 7.2 miles per hour, while on July 13, the calmest day of the year, the daily average wind speed is 4.3 miles per hour. The hourly average wind direction at Eielson Air Force Base throughout April is predominantly from the east, with a peak proportion of 48% on April 1. 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 at Eielson Air Force Base typically lasts for 3.8 months (115 days), from around May 13 to around September 6, rarely starting before April 29 or after May 29, and rarely ending before August 17 or after September 25. The month of April at Eielson Air Force Base is more likely than not fully outside of the growing season, with the chance that a given day is in the growing season increasing from 0% to 13% over the course of the month. 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 at Eielson Air Force Base are essentially constant during April, remaining within 10°F of 10°F throughout. 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 at Eielson Air Force Base is increasing during April, rising by 1.4 kWh, from 3.2 kWh to 4.6 kWh, over the course of the month. TopographyFor the purposes of this report, the geographical coordinates of Eielson Air Force Base are 64.664 deg latitude, -147.099 deg longitude, and 541 ft elevation. The topography within 2 miles of Eielson Air Force Base is essentially flat, with a maximum elevation change of 56 feet and an average elevation above sea level of 540 feet. Within 10 miles is essentially flat (1,522 feet). Within 50 miles contains very significant variations in elevation (6,076 feet). The area within 2 miles of Eielson Air Force Base is covered by trees (51%), sparse vegetation (30%), and artificial surfaces (12%), within 10 miles by trees (75%), and within 50 miles by trees (68%) and shrubs (21%). Data SourcesThis report illustrates the typical weather at Eielson Air Force Base, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointEielson Air Force Base has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required. In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations. The stations on which we may fall back are Fairbanks International Airport, Allen Army Air Field, Nenana Municipal Airport, and McKinley National Park Airport. 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. 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