Summer Weather in U.S. Virgin Islands U.S. Virgin IslandsDaily high temperatures are around 88°F, rarely falling below 85°F or exceeding 93°F. The highest daily average high temperature is 89°F on August 6. Daily low temperatures are around 79°F, rarely falling below 76°F or exceeding 82°F. The highest daily average low temperature is 80°F on August 7. For reference, on August 5, the hottest day of the year, temperatures in U.S. Virgin Islands typically range from 79°F to 89°F, while on January 21, the coldest day of the year, they range from 74°F to 83°F. The figure below shows you a compact characterization of the hourly average summer 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. CloudsThe summer in U.S. Virgin Islands experiences gradually decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 71% to 64%. The clearest day of the summer is July 31, with clear, mostly clear, or partly cloudy conditions 44% of the time. For reference, on May 29, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 72%, while on January 11, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 83%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In U.S. Virgin Islands, the chance of a wet day over the course of the summer is rapidly increasing, starting the season at 30% and ending it at 36%. For reference, the year's highest daily chance of a wet day is 39% on September 19, and its lowest chance is 12% on March 8. 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 summer in U.S. Virgin Islands is increasing, starting the season at 2.4 inches, when it rarely exceeds 5.5 inches or falls below 0.5 inches, and ending the season at 3.1 inches, when it rarely exceeds 6.1 inches or falls below 0.9 inches. The lowest average 31-day accumulation is 1.5 inches on June 29. SunOver the course of the summer in U.S. Virgin Islands, the length of the day is decreasing. From the start to the end of the season, the length of the day decreases by 41 minutes, implying an average daily decrease of 27 seconds, and weekly decrease of 3 minutes, 8 seconds. The shortest day of the summer is August 31, with 12 hours, 29 minutes of daylight and the longest day is June 20, with 13 hours, 14 minutes of daylight. The earliest sunrise of the summer in U.S. Virgin Islands is 5:42 AM on June 5 and the latest sunrise is 22 minutes later at 6:05 AM on August 31. The latest sunset is 7:00 PM on July 5 and the earliest sunset is 26 minutes earlier at 6:34 PM on August 31. Daylight saving time is not observed in U.S. Virgin Islands during 2024. For reference, on June 20, the longest day of the year, the Sun rises at 5:44 AM and sets 13 hours, 14 minutes later, at 6:58 PM, while on December 21, the shortest day of the year, it rises at 6:47 AM and sets 11 hours, 2 minutes later, at 5:49 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 summer 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 U.S. Virgin Islands is essentially constant during the summer, remaining within 1% of 98% throughout. The highest chance of a muggy day during the summer is 100% on August 1. For reference, on July 31, the muggiest day of the year, there are muggy conditions 100% of the time, while on March 1, the least muggy day of the year, there are muggy conditions 71% 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 in U.S. Virgin Islands is essentially constant during the summer, remaining within 1.1 miles per hour of 14.9 miles per hour throughout. For reference, on July 13, the windiest day of the year, the daily average wind speed is 16.0 miles per hour, while on October 9, the calmest day of the year, the daily average wind speed is 11.8 miles per hour. The highest daily average wind speed during the summer is 16.0 miles per hour on July 14. The hourly average wind direction in U.S. Virgin Islands throughout the summer is predominantly from the east, with a peak proportion of 99% on July 14. Water TemperatureU.S. Virgin Islands 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 U.S. Virgin Islands is gradually increasing during the summer, rising by 2°F, from 82°F to 84°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). Temperatures in U.S. Virgin Islands are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year. 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 U.S. Virgin Islands are very rapidly increasing during the summer, increasing by 2,988°F, from 4,392°F to 7,380°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 U.S. Virgin Islands is essentially constant during the summer, remaining within 0.2 kWh of 5.6 kWh throughout. TopographyFor the purposes of this report, the geographical coordinates of U.S. Virgin Islands are 18.348 deg latitude, -64.983 deg longitude, and 0 ft elevation. The topography within 2 miles of U.S. Virgin Islands is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet). The area within 2 miles of U.S. Virgin Islands is covered by water (44%), trees (27%), and grassland (20%), within 10 miles by water (91%), and within 50 miles by water (96%). Data SourcesThis report illustrates the typical weather in U.S. Virgin Islands, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. The details of the data sources used for this report can be found on the Cyril E. King Airport page. 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. 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