Climate and Average Weather Year Round in Ann Arbor Michigan, United StatesIn Ann Arbor, the summers are warm; the winters are freezing, snowy, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 17°F to 84°F and is rarely below 1°F or above 92°F. Based on the tourism score, the best time of year to visit Ann Arbor for warm-weather activities is from mid June to early September. Average Temperature in Ann ArborThe warm season lasts for 3.7 months, from May 25 to September 16, with an average daily high temperature above 73°F. The hottest month of the year in Ann Arbor is July, with an average high of 83°F and low of 63°F. The cold season lasts for 3.3 months, from November 30 to March 7, with an average daily high temperature below 41°F. The coldest month of the year in Ann Arbor is January, with an average low of 19°F and high of 31°F.
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. Novopavlovsk, Russia (5,654 miles away) is the far-away foreign place with temperatures most similar to Ann Arbor (view comparison). CloudsIn 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 5.0 months, ending around October 31. The clearest month of the year in Ann Arbor is August, during which on average the sky is clear, mostly clear, or partly cloudy 67% of the time. The cloudier part of the year begins around October 31 and lasts for 7.0 months, ending around June 1. The cloudiest month of the year in Ann Arbor is January, during which on average the sky is overcast or mostly cloudy 64% of the time.
PrecipitationA 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 6.4 months, from March 27 to October 7, with a greater than 26% chance of a given day being a wet day. The month with the most wet days in Ann Arbor is July, with an average of 10.6 days with at least 0.04 inches of precipitation. The drier season lasts 5.6 months, from October 7 to March 27. The month with the fewest wet days in Ann Arbor is February, with an average of 5.5 days with at least 0.04 inches of precipitation. 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 11 months, from February 17 to January 16. The month with the most days of rain alone in Ann Arbor is July, with an average of 10.6 days. Snow alone is the most common for 1.1 months, from January 16 to February 17. The month with the most days of snow alone in Ann Arbor is January, with an average of 2.5 days.
RainfallTo 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 of the year. Ann Arbor experiences significant seasonal variation in monthly rainfall. Rain falls throughout the year in Ann Arbor. The month with the most rain in Ann Arbor is June, with an average rainfall of 2.9 inches. The month with the least rain in Ann Arbor is January, with an average rainfall of 0.8 inches.
SnowfallAs with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Ann Arbor experiences significant seasonal variation in monthly snowfall. The snowy period of the year lasts for 4.8 months, from November 15 to April 10, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Ann Arbor is February, with an average snowfall of 5.9 inches. The snowless period of the year lasts for 7.2 months, from April 10 to November 15. The least snow falls around July 19, with an average total accumulation of 0.0 inches.
SunThe length of the day in Ann Arbor varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 5 minutes of daylight; the longest day is June 20, with 15 hours, 17 minutes of daylight.
The earliest sunrise is at 5:57 AM on June 14, and the latest sunrise is 2 hours, 12 minutes later at 8:10 AM on November 2. The earliest sunset is at 5:02 PM on December 8, 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 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3. The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation. MoonThe figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. HumidityWe 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 3.7 months, from May 29 to September 19, during which time the comfort level is muggy, oppressive, or miserable at least 8% of the time. The month with the most muggy days in Ann Arbor is July, with 9.9 days that are muggy or worse. The least muggy day of the year is February 15, when muggy conditions are essentially unheard of.
WindThis 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 significant seasonal variation over the course of the year. The windier part of the year lasts for 7.1 months, from October 7 to May 12, with average wind speeds of more than 10.4 miles per hour. The windiest month of the year in Ann Arbor is January, with an average hourly wind speed of 12.7 miles per hour. The calmer time of year lasts for 4.9 months, from May 12 to October 7. The calmest month of the year in Ann Arbor is August, with an average hourly wind speed of 8.0 miles per hour.
The predominant average hourly wind direction in Ann Arbor varies throughout the year. The wind is most often from the south for 1.6 weeks, from September 3 to September 14, with a peak percentage of 30% on September 13. The wind is most often from the west for 12 months, from September 14 to September 3, with a peak percentage of 46% on January 1. Water TemperatureAnn 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 extreme seasonal variation over the course of the year. The time of year with warmer water lasts for 3.1 months, from June 20 to September 23, with an average temperature above 67°F. The month of the year in Ann Arbor with the warmest water is August, with an average temperature of 74°F. The time of year with cooler water lasts for 4.3 months, from December 5 to April 15, with an average temperature below 42°F. The month of the year in Ann Arbor with the coolest water is February, with an average temperature of 34°F.
Best Time of Year to VisitTo characterize how pleasant the weather is in Ann Arbor throughout the year, we compute two travel scores. The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Ann Arbor for general outdoor tourist activities is from mid June to early September, with a peak score in the second week of August. Tourism Score in Ann ArborThe beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Ann Arbor for hot-weather activities is from late June to mid August, with a peak score in the third week of July. Beach/Pool Score in Ann ArborMethodologyFor each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed. Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies. Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more. Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter. Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter. Growing SeasonDefinitions 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 24 to around October 14, rarely starting before April 7 or after May 12, and rarely ending before September 25 or after November 1. 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. Based on growing degree days alone, the first spring blooms in Ann Arbor should appear around April 16, only rarely appearing before April 1 or after April 30. Solar EnergyThis 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 extreme seasonal variation over the course of the year. The brighter period of the year lasts for 3.6 months, from May 2 to August 21, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest month of the year in Ann Arbor is June, with an average of 6.8 kWh. The darker period of the year lasts for 3.4 months, from November 2 to February 13, with an average daily incident shortwave energy per square meter below 2.6 kWh. The darkest month of the year in Ann Arbor is December, with an average of 1.5 kWh.
TopographyFor the purposes of this report, the geographical coordinates of Ann Arbor are 42.278 deg latitude, -83.741 deg longitude, and 873 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%). Data SourcesThis 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 PointThere 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:
To get a sense of how much these sources agree with each other, you can view a comparison of Ann Arbor and the stations that contribute to our estimates of its temperature history and climate. Please note that each source's contribution is adjusted for elevation and the relative change present in the MERRA-2 data. Other DataAll data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , 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 airports and weather stations are provided by AskGeo.com . Maps are © OpenStreetMap contributors. DisclaimerThe 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. Please review our full terms contained on our Terms of Service page. |