Average Weather in September in Grand Rapids Michigan, United States
Daily high temperatures decrease by 11°F, from 77°F to 66°F, rarely falling below 55°F or exceeding 86°F.
Daily low temperatures decrease by 10°F, from 59°F to 48°F, rarely falling below 37°F or exceeding 69°F.
For reference, on July 19, the hottest day of the year, temperatures in Grand Rapids typically range from 63°F to 83°F, while on January 29, the coldest day of the year, they range from 18°F to 30°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 Grand Rapids experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 34% to 39%.
The clearest day of the month is September 1, with clear, mostly clear, or partly cloudy conditions 66% of the time.
For reference, on January 7, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 69%, while on August 7, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 67%.
Cloud Cover Categories in September
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Grand Rapids, the chance of a wet day over the course of September is essentially constant, remaining around 31% throughout.
For reference, the year's highest daily chance of a wet day is 33% on May 24, and its lowest chance is 17% on February 8.
Probability of Precipitation in September
The average sliding 31-day rainfall during September in Grand Rapids is essentially constant, remaining about 3.1 inches throughout, and rarely exceeding 5.7 inches or falling below 1.2 inches.
The highest average 31-day accumulation is 3.3 inches on September 23.
Average Monthly Rainfall in September
Over the course of September in Grand Rapids, 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, 23 minutes, implying an average daily decrease of 2 minutes, 52 seconds, and weekly decrease of 20 minutes, 7 seconds.
The shortest day of the month is September 30, with 11 hours, 47 minutes of daylight and the longest day is September 1, with 13 hours, 10 minutes of daylight.
Hours of Daylight and Twilight in September
The earliest sunrise of the month in Grand Rapids is 7:07 AM on September 1 and the latest sunrise is 32 minutes later at 7:38 AM on September 30.
The latest sunset is 8:17 PM on September 1 and the earliest sunset is 52 minutes earlier at 7:25 PM on September 30.
Daylight saving time is observed in Grand Rapids 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 6:03 AM and sets 15 hours, 22 minutes later, at 9:25 PM, while on December 21, the shortest day of the year, it rises at 8:10 AM and sets 9 hours, 0 minutes later, at 5:11 PM.
Sunrise & Sunset with Twilight in September
The chance that a given day will be muggy in Grand Rapids is rapidly decreasing during September, falling from 22% to 4% over the course of the month.
For reference, on July 28, the muggiest day of the year, there are muggy conditions 36% 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
The average hourly wind speed in Grand Rapids is increasing during September, increasing from 8.6 miles per hour to 10.1 miles per hour over the course of the month.
For reference, on January 12, the windiest day of the year, the daily average wind speed is 12.6 miles per hour, while on August 3, the calmest day of the year, the daily average wind speed is 7.8 miles per hour.
Average Wind Speed in September
Wind Direction in September
Grand Rapids is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average surface water temperature in Grand Rapids is decreasing during September, falling by 7°F, from 70°F to 62°F, over the course of the month.
Average Water Temperature in September
The growing season in Grand Rapids typically lasts for 5.5 months (167 days), from around April 29 to around October 13, rarely starting before April 11 or after May 18, and rarely ending before September 26 or after October 31.
The month of September in Grand Rapids is more likely than not fully within the growing season, with the chance that a given day is in the growing season decreasing from 100% to 83% 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 Grand Rapids are increasing during September, increasing by 382°F, from 2,353°F to 2,734°F, over the course of the month.
Growing Degree Days in September
The average daily incident shortwave solar energy in Grand Rapids is decreasing during September, falling by 1.4 kWh, from 5.5 kWh to 4.1 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 Grand Rapids are 42.963 deg latitude, -85.668 deg longitude, and 686 ft elevation.
The topography within 2 miles of Grand Rapids contains only modest variations in elevation, with a maximum elevation change of 197 feet and an average elevation above sea level of 666 feet. Within 10 miles also contains only modest variations in elevation (318 feet). Within 50 miles contains only modest variations in elevation (787 feet).
The area within 2 miles of Grand Rapids is covered by artificial surfaces (100%), within 10 miles by artificial surfaces (61%) and cropland (21%), and within 50 miles by cropland (44%) and trees (31%).
This report illustrates the typical weather in Grand Rapids 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 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Grand Rapids.
For each station, the records are corrected for the elevation difference between that station and Grand Rapids 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 Grand Rapids is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Grand Rapids and a given station.
The stations contributing to this reconstruction are: Gerald R. Ford International Airport (67%, 15 kilometers, southeast); West Michigan Regional Airport (14%, 43 kilometers, southwest); Muskegon County Airport (11%, 52 kilometers, northwest); and Fremont Municipal Airport (9%, 59 kilometers, northwest).
Time zones for aiports and weather stations are provided by AskGeo.com .