The superstitions for conjuring the snow-day cosmos on a blustery winter day are not to be taken lightly. Wearing your pajamas inside out is mandatory. Sleeping with a spoon under your pillow is non-negotiable. And flushing ice cubes down the toilet is absolutely required. On the meteorologic battlefield, no flake—or flannel onesie—can be left unturned.
Weather-related school closures are common across the country’s largest public districts, though some have canceled class vastly more often than others in the past decade. Where I grew up in the Chicago suburbs, teeth-chattering temperatures and back-breaking amounts of snow are practically inevitable, and the salt stains on my boots are proof enough that my hometown’s snow-related infrastructure is nothing if not thorough. Despite winter’s wrath, my high school has closed only a dozen or so times in the last 10 school years because of snow—a far cry from the 50 weather-related closures Jefferson County Public Schools in Louisville, Kentucky, had during the same timeframe. At an average of five weather-related closures each year, students in Louisville are typically left with a week of canceled courses annually.
Surely the regularity of its difficult weather poises the Chicagoland area to be more prepared for snow and ice than a place like Kentucky: Whereas the average winter temperature in Louisville is 37.2 degrees, it’s 26.4 degrees in Chicago, according to data from the National Oceanic and Atmospheric Association. Still, with its 50 closures, Louisville (which, granted, gets hit with quite a lot of rain and other Mother Nature-related disturbances) is the most-often-closed district that reported data to The Atlantic. And Jefferson County schools are far from residing in a league of their own: The public-school districts in Columbus, Ohio, and Oklahoma City closed for 42 and 43 days, respectively, over the last decade. Meanwhile, multiple large districts—from Billings Public Schools in Montana to the Los Angeles Unified School District—have closed either once or not at all in the same timeframe.
The frequency with which some districts around the country cancel classes warrants a closer look at closure policies. Districts have their own sets of guidelines for determining when the weather is too difficult to overcome, and while each area deals with specific forecasts and challenges, the variance between states is stark.
Many districts outline on their websites that a primary priority when considering a weather-based closure is the safety of students and faculty, but the ramifications of an unplanned day off extend past chilly toes and spilled cocoa. As Thomas Ahart, the superintendent of Des Moines Public Schools in Iowa, wrote in a note to district families, “I also consider the ripple effect a ‘snow day’ has on the entire community: not only for our 33,000 students and 5,000 employees but for tens of thousands of parents and family members, many of whom must go to work no matter the weather.” For many families, adverse weather conditions already make completing a day at work challenging; further deviations like school closures only add to the difficulties and stress of figuring out how to keep students safe and occupied. And on top of that, 94 percent of public schools offer breakfast to students, according to No Kid Hungry; when weather cancels classes, it also cancels a meal.
I reached out to the largest public school districts in the most populous cities in each state and asked them how often in the last 10 school years (2006-07 through 2015-16) they canceled classes because of weather. Not every district got back to me, and many reported that they don’t keep track of the closures year-over-year. Nineteen states sent over complete information, and their responses are represented in the map below. The eight places that only provided information from some years over the last decade are not included in the map, and the data represents all weather-related closures, not just those during the winter.
Although the dataset is incomplete, districts that did provide even anecdotal or partial data helped paint a picture that was generally pretty surprising. I expected states like Alaska and Utah, which receive a lot of snow, to have a reasonable number of closures each year. The task of quickly and effectively clearing roads buried under a foot of snow can be a challenging feat even for the strongest fleet of snowplows. However, over the last 10 years, Anchorage Public Schools in Alaska were closed for just eight days, and the Salt Lake City School District in Utah didn’t have a single weather-related closure during the Obama administration, according to a district spokesperson.
Additionally, because access to safe transportation is often a deciding factor in whether or not schools stay open, I assumed school districts in big metropolitan areas with sprawling public-transit systems would be less inclined to close. After all, in cities with robust train and subway networks, blocked bus routes and icy sidewalks seem less daunting. This proved to be true in New York City, where the public-school district canceled classes a total of just 11 days in the last 10 years, and Portland, Oregon, where district-wide closures have eaten just nine days off the calendar in the last nine years. On the other hand, Boston Public Schools had 19 weather-related closures in the past four school years, and in Washington, D.C., public schools have closed 14 times since the fall of 2012. The transit aspect may also be helpful in understanding why schools in a city like Baltimore—which has just one subway line and largely runs on buses—have closed 20 times for weather in the last three years.
Of course, natural disasters also resulted in distinctly regional trends: Districts up and down the Eastern seaboard—including those in Providence, Rhode Island; Virginia Beach, Virginia; and Wilmington, Delaware—closed because of Hurricane Sandy in October of 2012. Meanwhile, Tropical Storm Fay forced Duval County School District in Jacksonville, Florida, to cancel classes for three consecutive days in August of 2008.
Perhaps the most surprising finding, though, is that many districts were prone to long stretches of unexpected breaks. Columbus City Schools in Columbus, Ohio, for example, closed for at least two consecutive days during six of the last 10 school years. Meanwhile, in Oklahoma City, the public-school district closed down for four days in a row in January of 2007 and five additional consecutive days in December of the same year. These cancellations inevitably disrupt lesson plans and exams, though there is some research suggesting snow-day closures do not affect student academic performance.
Now, most school districts are winding down for some planned time off around the winter holidays—an anticipated break that’s well-earned. Still, there’s something truly magical about waking up to a 6 a.m. phone call, taking the spoon out from under your pillow, and using it to stir a giant mug of hot chocolate when you’re supposed to be in science class.
This post originally appeared on The Atlantic.