Winter Weather at Lan Yu TaiwanDaily high temperatures are around 71°F, rarely falling below 63°F or exceeding 78°F. The lowest daily average high temperature is 69°F on January 25. Daily low temperatures are around 65°F, rarely falling below 58°F or exceeding 71°F. The lowest daily average low temperature is 63°F on January 28. For reference, on July 9, the hottest day of the year, temperatures at Lan Yu typically range from 77°F to 83°F, while on January 28, the coldest day of the year, they range from 63°F to 69°F. The figure below shows you a compact characterization of the hourly average winter 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. Clémencia, Mauritius (5,209 miles away) and Nouméa, New Caledonia (4,308 miles) are the far-away foreign places with temperatures most similar to Lan Yu (view comparison). CloudsThe winter at Lan Yu experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 38% throughout the season. The lowest chance of overcast or mostly cloudy conditions is 36% on December 10. The clearest day of the winter is December 10, with clear, mostly clear, or partly cloudy conditions 64% of the time. For reference, on June 6, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 86%, while on December 10, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Lan Yu, the chance of a wet day over the course of the winter is essentially constant, remaining around 14% throughout. For reference, the year's highest daily chance of a wet day is 63% on August 17, and its lowest chance is 11% on December 27. 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 winter at Lan Yu is decreasing, starting the season at 1.3 inches, when it rarely exceeds 3.2 inches or falls below 0.1 inches, and ending the season at 0.8 inches, when it rarely exceeds 1.8 inches or falls below 0.1 inches. The lowest average 31-day accumulation is 0.6 inches on January 15. SunOver the course of the winter at Lan Yu, the length of the day is increasing. From the start to the end of the season, the length of the day increases by 48 minutes, implying an average daily increase of 33 seconds, and weekly increase of 3 minutes, 48 seconds. The shortest day of the winter is December 20, with 10 hours, 47 minutes of daylight and the longest day is February 28, with 11 hours, 41 minutes of daylight. The latest sunrise of the winter at Lan Yu is 6:35 AM on January 16 and the earliest sunrise is 19 minutes earlier at 6:15 AM on February 28. The earliest sunset is 5:09 PM on December 1 and the latest sunset is 48 minutes later at 5:57 PM on February 28. Daylight saving time is not observed at Lan Yu during 2024. For reference, on June 20, the longest day of the year, the Sun rises at 5:11 AM and sets 13 hours, 29 minutes later, at 6:39 PM, while on December 21, the shortest day of the year, it rises at 6:28 AM and sets 10 hours, 47 minutes later, at 5:15 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 winter 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 Lan Yu is decreasing during the winter, falling from 63% to 55% over the course of the season. The lowest chance of a muggy day during the winter is 37% on January 24. For reference, on June 13, the muggiest day of the year, there are muggy conditions 100% of the time, while on January 24, the least muggy day of the year, there are muggy conditions 37% 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 Lan Yu is very rapidly decreasing during the winter, decreasing from 21.0 miles per hour to 16.1 miles per hour over the course of the season. For reference, on December 1, the windiest day of the year, the daily average wind speed is 21.0 miles per hour, while on May 10, the calmest day of the year, the daily average wind speed is 12.8 miles per hour. The highest daily average wind speed during the winter is 21.0 miles per hour on December 1. The hourly average wind direction at Lan Yu throughout the winter is predominantly from the east, with a peak proportion of 70% on December 18. Water TemperatureLan Yu 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 Lan Yu is gradually decreasing during the winter, falling by 2°F, from 78°F to 76°F, over the course of the season. The lowest average surface water temperature during the winter is 76°F on January 31. 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 at Lan Yu 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 at Lan Yu are very rapidly decreasing during the winter, decreasing by 7,105°F, from 8,042°F to 938°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 Lan Yu is increasing during the winter, rising by 1.2 kWh, from 3.9 kWh to 5.1 kWh, over the course of the season. The lowest average daily incident shortwave solar energy during the winter is 3.7 kWh on December 24. TopographyFor the purposes of this report, the geographical coordinates of Lan Yu are 22.029 deg latitude, 121.534 deg longitude, and 39 ft elevation. The topography within 2 miles of Lan Yu contains very significant variations in elevation, with a maximum elevation change of 1,722 feet and an average elevation above sea level of 303 feet. Within 10 miles also contains very significant variations in elevation (1,722 feet). Within 50 miles contains very significant variations in elevation (2,986 feet). The area within 2 miles of Lan Yu is covered by water (95%), within 10 miles by water (100%), and within 50 miles by water (99%). Data SourcesThis report illustrates the typical weather at Lan Yu, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointLan Yu 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 Hengchun Airport, Chihhang Tw-Afb, Pingtung North Air Force Base, Pingtung South Air Force Base, Kaohsiung International Airport, Kangshan Tw-Afb, Tainan Airport, and Chiayi 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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