Average Weather in September in Mount Vernon Indiana, United States
Daily high temperatures decrease by 9°F, from 80°F to 71°F, rarely falling below 60°F or exceeding 89°F.
Daily low temperatures decrease by 10°F, from 61°F to 51°F, rarely falling below 40°F or exceeding 70°F.
For reference, on July 19, the hottest day of the year, temperatures in Mount Vernon typically range from 66°F to 84°F, while on January 29, the coldest day of the year, they range from 20°F to 34°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
Bucharest, Romania (5,208 miles away); Samashki, Russia (5,893 miles); and Damāvand, Iran (6,528 miles) are the far-away foreign places with temperatures most similar to Mount Vernon (view comparison).
The month of September in Mount Vernon experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 34% throughout the month.
The clearest day of the month is September 1, with clear, mostly clear, or partly cloudy conditions 68% of the time.
For reference, on January 2, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 61%, while on August 23, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 69%.
Cloud Cover Categories in September
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Mount Vernon, the chance of a wet day over the course of September is rapidly decreasing, starting the month at 31% and ending it at 24%.
For reference, the year's highest daily chance of a wet day is 41% on May 28, and its lowest chance is 18% on February 5.
Probability of Precipitation in September
The average sliding 31-day rainfall during September in Mount Vernon is gradually decreasing, starting the month at 3.1 inches, when it rarely exceeds 5.3 inches or falls below 1.1 inches, and ending the month at 2.7 inches, when it rarely exceeds 4.5 inches or falls below 1.2 inches.
Average Monthly Rainfall in September
Over the course of September in Mount Vernon, 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, 17 minutes, implying an average daily decrease of 2 minutes, 39 seconds, and weekly decrease of 18 minutes, 33 seconds.
The shortest day of the month is September 30, with 11 hours, 48 minutes of daylight and the longest day is September 1, with 13 hours, 5 minutes of daylight.
Hours of Daylight and Twilight in September
The earliest sunrise of the month in Mount Vernon is 7:10 AM on September 1 and the latest sunrise is 28 minutes later at 7:38 AM on September 30.
The latest sunset is 8:15 PM on September 1 and the earliest sunset is 48 minutes earlier at 7:26 PM on September 30.
Daylight saving time is observed in Mount Vernon during 2018, 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 6:12 AM and sets 15 hours, 5 minutes later, at 9:17 PM, while on December 21, the shortest day of the year, it rises at 8:03 AM and sets 9 hours, 15 minutes later, at 5:19 PM.
Sunrise & Sunset with Twilight in September
The chance that a given day will be muggy in Mount Vernon is very rapidly decreasing during September, falling from 29% to 5% over the course of the month.
For reference, on July 27, the muggiest day of the year, there are muggy conditions 48% of the time, while on November 16, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in September
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Mount Vernon is increasing during September, increasing from 7.8 miles per hour to 9.3 miles per hour over the course of the month.
For reference, on January 15, the windiest day of the year, the daily average wind speed is 12.6 miles per hour, while on August 4, the calmest day of the year, the daily average wind speed is 7.1 miles per hour.
Average Wind Speed in September
Wind Direction in September
The growing season in Mount Vernon typically lasts for 6.3 months (191 days), from around April 14 to around October 23, rarely starting before March 27 or after May 3, and rarely ending before October 2 or after November 14.
The month of September in Mount Vernon is very likely fully within the growing season, with the chance that a given day is in the growing season gradually decreasing from 100% to 93% over the course of the month.
Time Spent in Various Temperature Bands and the Growing Season in September
The average accumulated growing degree days in Mount Vernon are rapidly increasing during September, increasing by 459°F, from 2,689°F to 3,148°F, over the course of the month.
Growing Degree Days in September
The average daily incident shortwave solar energy in Mount Vernon is decreasing during September, falling by 1.2 kWh, from 5.7 kWh to 4.4 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 Mount Vernon are 40.669 deg latitude, -85.824 deg longitude, and 794 ft elevation.
The topography within 2 miles of Mount Vernon contains only modest variations in elevation, with a maximum elevation change of 108 feet and an average elevation above sea level of 778 feet. Within 10 miles also contains only modest variations in elevation (292 feet). Within 50 miles contains only modest variations in elevation (699 feet).
The area within 2 miles of Mount Vernon is covered by cropland (62%) and trees (27%), within 10 miles by cropland (88%), and within 50 miles by cropland (92%).
This report illustrates the typical weather in Mount Vernon 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 5 weather stations near enough to contribute to our estimation of the temperature and dew point in Mount Vernon.
For each station, the records are corrected for the elevation difference between that station and Mount Vernon 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 Mount Vernon is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Mount Vernon and a given station.
The stations contributing to this reconstruction are: Marion Municipal Airport (31%, 24 kilometers, southeast); Kokomo Municipal Airport (28%, 25 kilometers, southwest); Grissom Air Force Base / Peru (25%, 28 kilometers, west); Fulton County Airport (9%, 53 kilometers, northwest); and Fort Wayne International Airport (7%, 62 kilometers, northeast).
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.
Time zones for aiports and weather stations are provided by AskGeo.com .