Average Weather in September in Greenfield Iowa, United States
Daily high temperatures decrease by 10°F, from 80°F to 70°F, rarely falling below 58°F or exceeding 90°F.
Daily low temperatures decrease by 12°F, from 60°F to 48°F, rarely falling below 36°F or exceeding 69°F.
For reference, on July 20, the hottest day of the year, temperatures in Greenfield typically range from 66°F to 85°F, while on January 20, the coldest day of the year, they range from 16°F to 32°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
Çalxanqala, Azerbaijan (6,318 miles away); Yangquan, China (6,696 miles); and Koksan, North Korea (6,335 miles) are the far-away foreign places with temperatures most similar to Greenfield (view comparison).
The month of September in Greenfield experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 31% throughout the month.
The clearest day of the month is September 14, with clear, mostly clear, or partly cloudy conditions 71% of the time.
For reference, on February 12, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 53%, while on August 26, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 72%.
Cloud Cover Categories in September
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Greenfield, the chance of a wet day over the course of September is decreasing, starting the month at 31% and ending it at 25%.
For reference, the year's highest daily chance of a wet day is 44% on June 7, and its lowest chance is 8% on January 12.
Probability of Precipitation in September
The average sliding 31-day rainfall during September in Greenfield is decreasing, starting the month at 3.3 inches, when it rarely exceeds 6.4 inches or falls below 1.2 inches, and ending the month at 2.7 inches, when it rarely exceeds 4.8 inches or falls below 0.8 inches.
Average Monthly Rainfall in September
Over the course of September in Greenfield, 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, 19 minutes, implying an average daily decrease of 2 minutes, 43 seconds, and weekly decrease of 18 minutes, 58 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, 6 minutes of daylight.
Hours of Daylight and Twilight in September
The earliest sunrise of the month in Greenfield is 6:44 AM on September 1 and the latest sunrise is 29 minutes later at 7:13 AM on September 30.
The latest sunset is 7:50 PM on September 1 and the earliest sunset is 49 minutes earlier at 7:01 PM on September 30.
Daylight saving time is observed in Greenfield 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 5:44 AM and sets 15 hours, 10 minutes later, at 8:54 PM, while on December 21, the shortest day of the year, it rises at 7:40 AM and sets 9 hours, 11 minutes later, at 4:51 PM.
Sunrise & Sunset with Twilight in September
The chance that a given day will be muggy in Greenfield is very rapidly decreasing during September, falling from 34% to 4% over the course of the month.
For reference, on July 22, the muggiest day of the year, there are muggy conditions 57% 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
The average hourly wind speed in Greenfield is increasing during September, increasing from 9.2 miles per hour to 10.7 miles per hour over the course of the month.
For reference, on April 1, the windiest day of the year, the daily average wind speed is 13.0 miles per hour, while on August 3, the calmest day of the year, the daily average wind speed is 8.2 miles per hour.
Average Wind Speed in September
Wind Direction in September
The growing season in Greenfield typically lasts for 5.8 months (176 days), from around April 18 to around October 11, rarely starting before April 1 or after May 5, and rarely ending before September 22 or after October 31.
The month of September in Greenfield is more likely than not fully within the growing season, with the chance that a given day is in the growing season rapidly decreasing from 100% to 76% 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 Greenfield are increasing during September, increasing by 423°F, from 2,630°F to 3,053°F, over the course of the month.
Growing Degree Days in September
The average daily incident shortwave solar energy in Greenfield is decreasing during September, falling by 1.2 kWh, from 5.7 kWh to 4.5 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 Greenfield are 41.305 deg latitude, -94.461 deg longitude, and 1,319 ft elevation.
The topography within 2 miles of Greenfield contains only modest variations in elevation, with a maximum elevation change of 171 feet and an average elevation above sea level of 1,323 feet. Within 10 miles also contains only modest variations in elevation (364 feet). Within 50 miles contains only modest variations in elevation (784 feet).
The area within 2 miles of Greenfield is covered by cropland (91%), within 10 miles by cropland (95%), and within 50 miles by cropland (92%).
This report illustrates the typical weather in Greenfield 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 Greenfield.
For each station, the records are corrected for the elevation difference between that station and Greenfield 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 Greenfield is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Greenfield and a given station.
The stations contributing to this reconstruction are: Creston Municipal Airport (37%, 34 kilometers, south); Atlantic Municipal Airport (21%, 50 kilometers, west); Audubon County Airport (17%, 58 kilometers, northwest); Perry Municipal Airport (14%, 63 kilometers, northeast); and Des Moines International Airport (12%, 72 kilometers, east).
Time zones for aiports and weather stations are provided by AskGeo.com .