September Weather at McCarran International Airport Nevada, United StatesDaily high temperatures decrease by 10°F, from 99°F to 89°F, rarely falling below 79°F or exceeding 105°F. Daily low temperatures decrease by 11°F, from 76°F to 66°F, rarely falling below 57°F or exceeding 83°F. For reference, on July 13, the hottest day of the year, temperatures at McCarran International Airport typically range from 81°F to 104°F, while on December 26, the coldest day of the year, they range from 39°F to 56°F. The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. 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. Béchar, Algeria (6,064 miles away); Berriane, Algeria (6,261 miles); and Hajīn, Syria (7,316 miles) are the far-away foreign places with temperatures most similar to McCarran International Airport (view comparison). CloudsThe month of September at McCarran International Airport experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 14% throughout the month. The lowest chance of overcast or mostly cloudy conditions is 13% on September 17. The clearest day of the month is September 17, with clear, mostly clear, or partly cloudy conditions 87% of the time. For reference, on February 19, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 39%, while on June 20, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 88%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At McCarran International Airport, the chance of a wet day over the course of September is gradually decreasing, starting the month at 8% and ending it at 4%. For reference, the year's highest daily chance of a wet day is 13% on February 22, and its lowest chance is 1% on June 15. RainfallTo 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 September at McCarran International Airport is essentially constant, remaining about 0.4 inches throughout, and rarely exceeding 1.1 inches. The lowest average 31-day accumulation is 0.3 inches on September 30. SunOver the course of September at McCarran International Airport, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 5 minutes, implying an average daily decrease of 2 minutes, 15 seconds, and weekly decrease of 15 minutes, 44 seconds. The shortest day of the month is September 30, with 11 hours, 49 minutes of daylight and the longest day is September 1, with 12 hours, 54 minutes of daylight. The earliest sunrise of the month at McCarran International Airport is 6:12 AM on September 1 and the latest sunrise is 23 minutes later at 6:35 AM on September 30. The latest sunset is 7:07 PM on September 1 and the earliest sunset is 43 minutes earlier at 6:24 PM on September 30. Daylight saving time is observed at McCarran International Airport during 2024, but it neither starts nor ends during September, so the entire month is in daylight saving time. For reference, on June 20, the longest day of the year, the Sun rises at 5:23 AM and sets 14 hours, 37 minutes later, at 8:00 PM, while on December 21, the shortest day of the year, it rises at 6:47 AM and sets 9 hours, 42 minutes later, at 4:30 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 September 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 McCarran International Airport is gradually decreasing during September, falling from 3% to 0% over the course of the month. For reference, on August 15, the muggiest day of the year, there are muggy conditions 3% of the time, while on October 12, 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 McCarran International Airport is essentially constant during September, remaining within 0.1 miles per hour of 7.2 miles per hour throughout. For reference, on April 25, the windiest day of the year, the daily average wind speed is 9.4 miles per hour, while on August 27, the calmest day of the year, the daily average wind speed is 7.1 miles per hour. The wind direction at McCarran International Airport during September is predominantly out of the south from September 1 to September 24 and the north from September 24 to September 30. 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 McCarran International Airport typically lasts for 11 months (321 days), from around January 22 to around December 8, rarely starting after February 20, or ending before November 18. The month of September at McCarran International Airport 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 McCarran International Airport are rapidly increasing during September, increasing by 864°F, from 5,018°F to 5,882°F, over the course of the month. 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 McCarran International Airport is decreasing during September, falling by 1.1 kWh, from 6.8 kWh to 5.7 kWh, over the course of the month. TopographyFor the purposes of this report, the geographical coordinates of McCarran International Airport are 36.085 deg latitude, -115.151 deg longitude, and 2,093 ft elevation. The topography within 2 miles of McCarran International Airport contains only modest variations in elevation, with a maximum elevation change of 253 feet and an average elevation above sea level of 2,094 feet. Within 10 miles contains only modest variations in elevation (2,129 feet). Within 50 miles contains large variations in elevation (11,234 feet). The area within 2 miles of McCarran International Airport is covered by shrubs (65%), artificial surfaces (20%), and bare soil (15%), within 10 miles by shrubs (65%) and artificial surfaces (32%), and within 50 miles by shrubs (91%). Data SourcesThis report illustrates the typical weather at McCarran International 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 PointMcCarran International 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 include but are not limited to Henderson Executive Airport, North Las Vegas Air Terminal, Nellis Air Force Base, Boulder City Municipal Airport, Creech Air Force Base, Desert Rock Airport, Laughlin/Bullhead International Airport, and Bicycle Lake Army Airfield. 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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