April Weather in Unalaska United States

Daily high temperatures increase by 3°F, from 38°F to 41°F, rarely falling below 32°F or exceeding 46°F.

Daily low temperatures increase by 4°F, from 32°F to 36°F, rarely falling below 26°F or exceeding 39°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.

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.

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 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 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%.

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 very 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 16, and its lowest chance is 25% on May 4.

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.

Rainfall

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 3.3 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 24.

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 April in Unalaska is decreasing, starting the month at 1.6 inches, when it rarely exceeds 4.6 inches or falls below -0.0 inches, and ending the month at 0.2 inches, when it rarely exceeds 0.7 inches or falls below -0.0 inches.

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, 1 second.

The shortest day of the month is April 1, with 13 hours, 7 minutes of daylight and the longest day is April 30, with 15 hours, 7 minutes of daylight.

The latest sunrise of the month in Unalaska is 7:37 AM on April 1 and the earliest sunrise is 1 hour, 7 minutes earlier at 6:30 AM on April 30.

The earliest sunset is 8:43 PM on April 1 and the latest sunset is 54 minutes later at 9:37 PM on April 30.

Daylight saving time is observed in Unalaska 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 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.

The 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.

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.

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 15.8 miles per hour over the course of the month.

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 hourly average wind direction in Unalaska throughout April is predominantly from the north, with a peak proportion of 34% on April 19.

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.

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 April in Unalaska, the chance that a given day is within the growing season is very rapidly increasing rising from 5% to 56% 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 in Unalaska are essentially constant during April, remaining around 0°F throughout.

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 4.2 kWh, over the course of the month.