Washtenaw County
Ann Arbor is a place where two separate decisions get made in the same storm: the school district's and the university's. The estimate below is loaded with live Ann Arbor forecast data.
Live Ann Arbor forecast estimate
Enter a location to compare tomorrow's snow, ice, temperature, wind and morning timing.
Local conditions
Ann Arbor sits inland in southeast Michigan, in the Huron River valley and well away from the lake-effect belt on the state's western side. Winter weather arrives with organised systems, frequently including a warmer layer aloft that produces sleet and freezing rain. The valley setting encourages cold air to settle overnight, which favours refreeze on wet surfaces and morning icing. The surrounding county mixes compact city streets with genuinely rural township roads, so conditions inside one district can vary more than the small distances suggest.
What actually drives a decision
Ann Arbor Public Schools and the University of Michigan make independent operating decisions. A cancelled class schedule on campus does not close the district, and a district closure does not close the university. If you need the campus answer, use the college setting and check the university's own emergency alert system.
Cold air settling in the river valley overnight can turn wet pavement into black ice by dawn with no new precipitation. Read the minimum temperature alongside the previous day's rain or melt rather than looking only at forecast snowfall.
Washtenaw County districts frequently combine dense city neighbourhoods with long rural stretches. The rural portion is treated later and is more exposed to drifting, which is why a district can be weighing very different conditions across one bus network.
Systems tracking up from the Ohio Valley bring the region's most disruptive events. Because ice produces no depth, an icing forecast can look minor while being the outcome most likely to stop transportation.
The forecast for the coordinates above is scored against six weighted factors: snow and ice, temperature, wind chill, morning timing, area and routes, and school level. Around Ann Arbor the rows that most often carry the number are temperature, snow and ice, school level. Every factor appears in the result with its own value, score bar and published weight, so a percentage is never presented without the reasoning behind it. The methodology page documents each threshold, and the accuracy and limitations page sets out what the model cannot observe.
This site does not publish closure thresholds for any school system, because those are operational judgements rather than published numbers. What it can do is point you at the organisations that actually decide. Around Ann Arbor, MI those include:
Treat the estimate on this page as a reason to prepare and to keep checking, never as an announcement. A school system can close buildings, delay the start, cancel transportation only, dismiss early or move to a different learning format, and those outcomes are not interchangeable.
Primary sources for weather warnings and road conditions covering Ann Arbor. School decisions still come from the systems listed above.
Ann Arbor questions
This page estimates weather pressure only, and in Ann Arbor there are two answers to look for. Ann Arbor Public Schools announces through its own family channels; the University of Michigan publishes a separate operating status that has no bearing on the district.
No. The university and the school district are separate authorities with separate criteria and separate announcements. It is normal for one to change operations while the other does not.
Select College as the school level, or open the college snow day calculator where that setting is preselected. Then compare the estimate with the university's official emergency alert and operating status page.
Match the school's road network. City schools fit Urban; districts covering township roads outside the city are better represented by Suburban or Rural, which the model treats as having longer and later-treated routes.
Still deciding what to do with the number? Read how schools make the final call and the guide to the best times to check a forecast.