Summer Weather at Osan Ab South KoreaDaily high temperatures increase by 4°F, from 78°F to 82°F, rarely falling below 70°F or exceeding 93°F. The highest daily average high temperature is 87°F on August 3. Daily low temperatures increase by 7°F, from 60°F to 67°F, rarely falling below 54°F or exceeding 78°F. The highest daily average low temperature is 73°F on August 3. For reference, on August 3, the hottest day of the year, temperatures at Osan Ab typically range from 73°F to 87°F, while on January 19, the coldest day of the year, they range from 17°F to 35°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. Kahoka, United States (6,553 miles away) is the far-away foreign place with temperatures most similar to Osan Ab (view comparison). CloudsThe summer at Osan Ab experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 50% throughout the season. The highest chance of overcast or mostly cloudy conditions is 56% on July 12. The clearest day of the summer is June 1, with clear, mostly clear, or partly cloudy conditions 56% of the time. For reference, on July 12, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 56%, while on October 19, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 71%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Osan Ab, the chance of a wet day over the course of the summer is very rapidly increasing, starting the season at 19% and ending it at 39%. For reference, the year's highest daily chance of a wet day is 51% on July 25, and its lowest chance is 8% on January 23. 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 at Osan Ab is very rapidly increasing, starting the season at 3.6 inches, when it rarely exceeds 6.6 inches or falls below 1.2 inches, and ending the season at 8.1 inches, when it rarely exceeds 16.4 inches or falls below 1.8 inches. The highest average 31-day accumulation is 10.9 inches on July 15. SunOver the course of the summer at Osan Ab, the length of the day is rapidly decreasing. From the start to the end of the season, the length of the day decreases by 1 hour, 33 minutes, implying an average daily decrease of 1 minute, 1 second, and weekly decrease of 7 minutes, 7 seconds. The shortest day of the summer is August 31, with 13 hours, 0 minutes of daylight and the longest day is June 21, with 14 hours, 43 minutes of daylight. The earliest sunrise of the summer at Osan Ab is 5:11 AM on June 13 and the latest sunrise is 50 minutes later at 6:01 AM on August 31. The latest sunset is 7:55 PM on June 28 and the earliest sunset is 54 minutes earlier at 7:01 PM on August 31. Daylight saving time is not observed at Osan Ab during 2024. For reference, on June 20, the longest day of the year, the Sun rises at 5:12 AM and sets 14 hours, 43 minutes later, at 7:54 PM, while on December 21, the shortest day of the year, it rises at 7:41 AM and sets 9 hours, 37 minutes later, at 5:18 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 at Osan Ab is very rapidly increasing during the summer, rising from 13% to 63% over the course of the season. The highest chance of a muggy day during the summer is 94% on August 2. For reference, on August 2, the muggiest day of the year, there are muggy conditions 94% 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 Osan Ab is essentially constant during the summer, remaining within 0.5 miles per hour of 7.2 miles per hour throughout. For reference, on February 24, the windiest day of the year, the daily average wind speed is 9.6 miles per hour, while on June 13, the calmest day of the year, the daily average wind speed is 6.7 miles per hour. The lowest daily average wind speed during the summer is 6.7 miles per hour on June 13. The wind direction at Osan Ab during the summer is predominantly out of the west from June 1 to July 9, the south from July 9 to August 9, and the east from August 9 to August 31. Water TemperatureOsan Ab 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 at Osan Ab is very rapidly increasing during the summer, rising by 16°F, from 59°F to 75°F, over the course of the season. The highest average surface water temperature during the summer is 76°F on August 20. 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 Osan Ab typically lasts for 6.6 months (203 days), from around April 7 to around October 27, rarely starting before March 23 or after April 22, and rarely ending before October 12 or after November 11. The summer at Osan Ab is reliably fully within the growing season. 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 Osan Ab are very rapidly increasing during the summer, increasing by 2,305°F, from 652°F to 2,957°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 at Osan Ab is decreasing during the summer, falling by 1.5 kWh, from 6.5 kWh to 5.1 kWh, over the course of the season. TopographyFor the purposes of this report, the geographical coordinates of Osan Ab are 37.091 deg latitude, 127.030 deg longitude, and 33 ft elevation. The topography within 2 miles of Osan Ab contains only modest variations in elevation, with a maximum elevation change of 256 feet and an average elevation above sea level of 61 feet. Within 10 miles contains only modest variations in elevation (1,102 feet). Within 50 miles contains very significant variations in elevation (4,032 feet). The area within 2 miles of Osan Ab is covered by sparse vegetation (39%), cropland (25%), trees (22%), and grassland (14%), within 10 miles by cropland (37%) and trees (30%), and within 50 miles by trees (32%) and cropland (20%). Data SourcesThis report illustrates the typical weather at Osan Ab, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointOsan Ab 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 include but are not limited to Pyongtaek Ab, Suwon Ab, Seoul Air Base, Seoul, Gimpo International Airport, Cheongju International Airport, Mangilsan Ab, and Camp Stanley / H-207. 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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