Average Weather in September in Las Vegas Nevada, United States
In Las Vegas, the month of September is characterized by rapidly falling daily high temperatures, with daily highs decreasing by 10°F, from 99°F to 89°F over the course of the month, and rarely exceeding 105°F or dropping below 80°F.
Daily low temperatures decrease by 10°F, from 76°F to 65°F, rarely falling below 57°F or exceeding 82°F.
For reference, on July 13, the hottest day of the year, temperatures in Las Vegas typically range from 80°F to 105°F, while on December 26, the coldest day of the year, they range from 38°F to 56°F.
Average High and Low Temperature in September
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.
Average Hourly Temperature in September
The month of September in Las Vegas 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 12% on September 18.
The clearest day of the month is September 18, with clear, mostly clear, or partly cloudy conditions 88% of the time.
For reference, on February 23, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 39%, while on June 21, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 88%.
Cloud Cover in September
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Las Vegas, 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 16.
Probability of Precipitation in September
To 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 in Las Vegas is essentially constant, remaining about 0.3 inches throughout, and rarely exceeding 1.1 inches or falling below -0.0 inches.
Average Monthly Rainfall in September
Over the course of September in Las Vegas, 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, 48 seconds.
The shortest day of the month is September 30, with 11 hours, 50 minutes of daylight and the longest day is September 1, with 12 hours, 55 minutes of daylight.
Hours of Daylight and Twilight in September
The earliest sunrise of the month in Las Vegas 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 6:25 PM on September 30.
Daylight saving time is observed in Las Vegas during 2017, but it neither starts nor ends during September, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:23 AM and sets 14 hours, 37 minutes later, at 8:01 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 4:29 PM.
Sunrise & Sunset with Twilight in September
We 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 Las Vegas is gradually decreasing during September, falling from 3% to 0% over the course of the month.
For reference, on August 6, the muggiest day of the year, there are muggy conditions 4% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in September
This 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 Las Vegas is essentially constant during September, remaining around 3.9 miles per hour throughout.
For reference, on April 26, the windiest day of the year, the daily average wind speed is 5.0 miles per hour, while on August 28, the calmest day of the year, the daily average wind speed is 3.8 miles per hour.
Average Wind Speed in September
Wind Direction in September
This 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 Las Vegas is decreasing during September, falling by 1.1 kWh, from 6.8 kWh to 5.7 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in September
For the purposes of this report, the geographical coordinates of Las Vegas are 36.175 deg latitude, -115.137 deg longitude, and 1,985 ft elevation.
The topography within 2 miles of Las Vegas contains only modest variations in elevation, with a maximum elevation change of 272 feet and an average elevation above sea level of 1,954 feet. Within 10 miles contains only modest variations in elevation (2,415 feet). Within 50 miles contains large variations in elevation (11,234 feet).
The area within 2 miles of Las Vegas is covered by artificial surfaces (53%) and shrubs (47%), within 10 miles by shrubs (59%) and artificial surfaces (32%), and within 50 miles by shrubs (91%).
This report illustrates the typical weather in Las Vegas year round, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Las Vegas.
For each station, the records are corrected for the elevation difference between that station and Las Vegas according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Las Vegas is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Las Vegas and a given station.
The stations contributing to this reconstruction are: North Las Vegas Air Terminal (45%, 7 kilometers, northwest); McCarran International Airport (27%, 12 kilometers, south); and Nellis Air Force Base (28%, 13 kilometers, northeast).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.