Average Weather in October in Ann Arbor Michigan, United States
In Ann Arbor, the month of October is characterized by rapidly falling daily high temperatures, with daily highs decreasing by 12°F, from 67°F to 55°F over the course of the month, and rarely exceeding 79°F or dropping below 42°F.
Daily low temperatures decrease by 9°F, from 48°F to 38°F, rarely falling below 28°F or exceeding 59°F.
For reference, on July 19, the hottest day of the year, temperatures in Ann Arbor typically range from 63°F to 84°F, while on January 29, the coldest day of the year, they range from 17°F to 31°F.
Average High and Low Temperature in October
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on October. 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 October
The month of October in Ann Arbor experiences increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 37% to 48%.
The clearest day of the month is October 1, with clear, mostly clear, or partly cloudy conditions 63% of the time.
For reference, on January 10, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 64%, while on August 23, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 67%.
Cloud Cover Categories in October
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Ann Arbor, the chance of a wet day over the course of October is decreasing, starting the month at 28% and ending it at 22%.
For reference, the year's highest daily chance of a wet day is 35% on June 15, and its lowest chance is 16% on February 2.
Probability of Precipitation in October
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 October in Ann Arbor is decreasing, starting the month at 2.6 inches, when it rarely exceeds 4.6 inches or falls below 1.2 inches, and ending the month at 2.1 inches, when it rarely exceeds 3.5 inches or falls below 0.8 inches.
Average Monthly Rainfall in October
Over the course of October in Ann Arbor, 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, 22 minutes, implying an average daily decrease of 2 minutes, 43 seconds, and weekly decrease of 19 minutes, 2 seconds.
The shortest day of the month is October 31, with 10 hours, 22 minutes of daylight and the longest day is October 1, with 11 hours, 44 minutes of daylight.
Hours of Daylight and Twilight in October
The earliest sunrise of the month in Ann Arbor is 7:32 AM on October 1 and the latest sunrise is 35 minutes later at 8:07 AM on October 31.
The latest sunset is 7:15 PM on October 1 and the earliest sunset is 47 minutes earlier at 6:29 PM on October 31.
Daylight saving time is observed in Ann Arbor during 2017, but it neither starts nor ends during October, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:58 AM and sets 15 hours, 17 minutes later, at 9:15 PM, while on December 21, the shortest day of the year, it rises at 8:00 AM and sets 9 hours, 5 minutes later, at 5:05 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in October
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 Ann Arbor is gradually decreasing during October, falling from 3% to 0% over the course of the month.
For reference, on August 1, the muggiest day of the year, there are muggy conditions 34% 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 October
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 Ann Arbor is increasing during October, increasing from 10.0 miles per hour to 11.2 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 12.8 miles per hour, while on August 4, the calmest day of the year, the daily average wind speed is 7.9 miles per hour.
Average Wind Speed in October
Wind Direction in October
Ann Arbor 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 Ann Arbor is rapidly decreasing during October, falling by 11°F, from 64°F to 53°F, over the course of the month.
Average Water Temperature in October
Definitions 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 in Ann Arbor typically lasts for 5.7 months (173 days), from around April 25 to around October 15, rarely starting before April 8 or after May 13, and rarely ending before September 26 or after November 2.
During October in Ann Arbor, the chance that a given day is within the growing season is very rapidly decreasing falling from 82% to 13% over the course of the month.
Time Spent in Various Temperature Bands and the Growing Season in October
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 in Ann Arbor is gradually increasing during October, increasing by 153°F, from 2,776°F to 2,929°F, over the course of the month.
Growing Degree Days in October
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 Ann Arbor is rapidly decreasing during October, falling by 1.5 kWh, from 4.2 kWh to 2.7 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in October
For the purposes of this report, the geographical coordinates of Ann Arbor are 42.278 deg latitude, -83.741 deg longitude, and 879 ft elevation.
The topography within 2 miles of Ann Arbor contains only modest variations in elevation, with a maximum elevation change of 243 feet and an average elevation above sea level of 861 feet. Within 10 miles also contains only modest variations in elevation (384 feet). Within 50 miles contains only modest variations in elevation (801 feet).
The area within 2 miles of Ann Arbor is covered by artificial surfaces (98%), within 10 miles by cropland (51%) and artificial surfaces (30%), and within 50 miles by cropland (49%) and artificial surfaces (24%).
This report illustrates the typical weather in Ann Arbor 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 Ann Arbor.
For each station, the records are corrected for the elevation difference between that station and Ann Arbor 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 Ann Arbor is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Ann Arbor and a given station.
The stations contributing to this reconstruction are: Willow Run Airport (54%, 18 kilometers, east); Livingston County Spencer J. Hardy Airport (14%, 44 kilometers, northwest); Oakland County International Airport (12%, 51 kilometers, northeast); Lenawee County Airport (11%, 53 kilometers, southwest); and Jackson County Airport (9%, 60 kilometers, west).
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.
The 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.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.