Fall Weather at Arusha Airport TanzaniaDaily high temperatures decrease by 11°F, from 83°F to 73°F, rarely falling below 69°F or exceeding 88°F. Daily low temperatures are around 61°F, rarely falling below 55°F or exceeding 65°F. The highest daily average low temperature is 63°F on April 4. For reference, on February 17, the hottest day of the year, temperatures at Arusha Airport typically range from 60°F to 83°F, while on July 13, the coldest day of the year, they range from 56°F to 71°F. The figure below shows you a compact characterization of the hourly average fall 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 fall at Arusha Airport experiences very rapidly decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 73% to 49%. The clearest day of the fall is May 31, with clear, mostly clear, or partly cloudy conditions 51% of the time. For reference, on February 2, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 76%, while on August 31, 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 Arusha Airport, the chance of a wet day over the course of the fall is rapidly decreasing, starting the season at 18% and ending it at 11%. For reference, the year's highest daily chance of a wet day is 45% on April 19, and its lowest chance is 1% on September 6. 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 fall at Arusha Airport is rapidly decreasing, starting the season at 1.9 inches, when it rarely exceeds 4.2 inches or falls below 0.1 inches, and ending the season at 0.8 inches, when it rarely exceeds 1.9 inches. The highest average 31-day accumulation is 4.4 inches on April 15. SunOver the course of the fall at Arusha Airport, the length of the day is essentially constant. The shortest day of the fall is May 31, with 11 hours, 56 minutes of daylight and the longest day is March 1, with 12 hours, 10 minutes of daylight. The latest sunrise of the fall at Arusha Airport is 6:40 AM on March 1 and the earliest sunrise is 10 minutes earlier at 6:30 AM on May 7. The latest sunset is 6:50 PM on March 1 and the earliest sunset is 22 minutes earlier at 6:28 PM on May 18. Daylight saving time is not observed at Arusha Airport during 2024. For reference, on December 21, the longest day of the year, the Sun rises at 6:22 AM and sets 12 hours, 19 minutes later, at 6:41 PM, while on June 20, the shortest day of the year, it rises at 6:37 AM and sets 11 hours, 56 minutes later, at 6:33 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 fall 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 Arusha Airport is decreasing during the fall, falling from 8% to 2% over the course of the season. The highest chance of a muggy day during the fall is 19% on April 8. For reference, on April 8, the muggiest day of the year, there are muggy conditions 19% of the time, while on July 28, 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 Arusha Airport is rapidly increasing during the fall, increasing from 5.9 miles per hour to 8.7 miles per hour over the course of the season. For reference, on September 24, the windiest day of the year, the daily average wind speed is 11.0 miles per hour, while on January 29, the calmest day of the year, the daily average wind speed is 5.3 miles per hour. The wind direction at Arusha Airport during the fall is predominantly out of the east from March 1 to May 27 and the south from May 27 to May 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 Arusha Airport 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 Arusha Airport are very rapidly increasing during the fall, increasing by 1,699°F, from 4,392°F to 6,091°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 Arusha Airport is gradually decreasing during the fall, falling by 0.5 kWh, from 6.8 kWh to 6.3 kWh, over the course of the season. The highest average daily incident shortwave solar energy during the fall is 6.9 kWh on March 4. TopographyFor the purposes of this report, the geographical coordinates of Arusha Airport are -3.368 deg latitude, 36.625 deg longitude, and 4,547 ft elevation. The topography within 2 miles of Arusha Airport 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 Arusha Airport is covered by cropland (99%), within 10 miles by cropland (57%) and grassland (17%), and within 50 miles by shrubs (34%) and grassland (25%). Data SourcesThis report illustrates the typical weather at Arusha Airport, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointArusha Airport 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 Kilimanjaro International Airport and Makindu 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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