How Much Snow Will Cancel School?

The decision to cancel school due to snow is not taken lightly, because schools have to complete a certain number of instruction days in a year. It’s usually a combination of school district topography, road conditions, and local snow-clearing systems. For example, where I live, the city school can get buses around in some snow, because the routes are only a few miles and the roads get salted. But the county schools have to send buses over long routes that are treacherous in good weather and are not maintained (often not even paved). Whether an area expects snow has a lot to do with how prepared they are to plow or salt roads. It is not cost-effective to buy and store snowplows and salt where it only snows once in a decade.  

Redditor atrubetskoy constructed a map that shows approximately how much snow is required to cancel school in the various parts of the U.S. See it full-size here. Read about the map and some of the data used at The Atlantic.