Average Weather in Ann Arbor Michigan, United States
In Ann Arbor, the temperature typically varies from 17°F to 84°F over the course of the year, and is rarely below 1°F or above 92°F.
The warm season lasts for 115 days, from May 26 to September 18, with an average daily high temperature above 73°F. The hottest day of the year is July 19, with an average high of 84°F and low of 63°F.
The cold season lasts for 98 days, from November 30 to March 8, with an average daily high temperature below 42°F. The coldest day of the year is January 29, with an average low of 17°F and high of 31°F.
Average High and Low Temperature
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature
The length of the day in Ann Arbor varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 5 minutes of daylight; the longest day is June 21, with 15 hours, 17 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:57 AM on June 14, and the latest sunrise is 2 hours, 14 minutes later at 8:12 AM on November 4. The earliest sunset is at 5:02 PM on December 7, and the latest sunset is 4 hours, 13 minutes later at 9:15 PM on June 26.
Daylight saving time (DST) is observed in Ann Arbor during 2017, starting in the spring on March 12, lasting 237 days, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
In Ann Arbor, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Ann Arbor begins around June 1 and lasts for 153 days, ending around November 1. On August 23, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 67% of the time, and overcast or mostly cloudy 33% of the time.
The cloudier part of the year begins around November 1 and lasts for 212 days, ending around June 1. On January 10, the cloudiest day of the year, the sky is overcast or mostly cloudy 64% of the time, and clear, mostly clear, or partly cloudy 36% of the time.
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Ann Arbor varies throughout the year.
The wetter season lasts 192 days, from March 29 to October 7, with a greater than 26% chance of a given day being a wet day. The chance of a wet day peaks at 35% on June 15.
The drier season lasts 173 days, from October 7 to March 29. The smallest chance of a wet day is 16% on February 2.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation in Ann Arbor changes throughout the year.
Rain alone is the most common for 333 days, from February 17 to January 16. The highest chance of a day with rain alone is 35% on June 15.
Snow alone is the most common for 32 days, from January 16 to February 17. The highest chance of a day with snow alone is 8% on January 15.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day in the year. Ann Arbor experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Ann Arbor. The most rain falls during the 31 days centered around June 2, with an average total accumulation of 3.0 inches.
The least rain falls around January 29, with and average total accumulation of 0.7 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day in the year. Ann Arbor experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 144 days, from November 17 to April 10, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around February 10, with an average total liquid-equivalent accumulation of 0.6 inches.
The snowless period of the year lasts for 221 days, from April 10 to November 17. The least snow falls around July 20, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
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.
Ann Arbor experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 113 days, from May 30 to September 20, during which time the comfort level is muggy, oppressive, or miserable at least 9% of the time. The muggiest day of the year is August 1, with muggy conditions 34% of the time.
The least muggy day of the year is February 15, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
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 experiences mildly seasonal variation over the course of the year.
The windier part of the year lasts for 217 days, from October 8 to May 13, with average wind speeds of more than 5.6 miles per hour. The windiest day of the year is January 15, with an average hourly wind speed of 6.9 miles per hour.
The calmer time of year lasts for 148 days, from May 13 to October 8. The calmest day of the year is August 4, with an average hourly wind speed of 4.3 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Ann Arbor varies throughout the year.
The wind is most often from the south for 11 days, from September 1 to September 12, with a peak percentage of 31% on November 14. The wind is most often from the west for 354 days, from September 12 to September 1, with a peak percentage of 47% on December 13.
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 water temperature experiences very significant seasonal variation over the course of the year.
The time of year with warmer water lasts for 96 days, from June 21 to September 25, with an average temperature above 66°F. The day of the year with the warmest water is August 4, with an average temperature of 75°F.
The time of year with cooler water lasts for 132 days, from December 6 to April 17, with an average temperature below 42°F. The day of the year with the coolest water is February 17, with an average temperature of 34°F.
Average Water Temperature
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 experiences very significant seasonal variation over the course of the year.
The brighter period of the year lasts for 112 days, from May 3 to August 23, with an average daily incident shortwave energy per square meter above 5.8 kWh. The brightest day of the year is July 1, with an average of 7.0 kWh.
The darker period of the year lasts for 103 days, from November 2 to February 13, with an average daily incident shortwave energy per square meter below 2.6 kWh. The darkest day of the year is December 20, with an average of 1.5 kWh.
Average Daily Incident Shortwave Solar Energy
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 (map ).
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 significant 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, 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 .