How to use the snow day calculator
- Pick your state or province, then the nearest area. That loads the area’s snow climate.
- Copy tonight’s forecast from your weather app: snow and its timing, freezing rain, morning temperature and wind.
- Describe your school. Rural districts with long bus routes close more readily than city districts where most students walk.
- Read the chance, its range and what moved it. Tap Share result to send it: the link holds your state or province, the area you picked (or the yearly snowfall you typed in) and your forecast and school answers, never your exact position.
How the calculator works
Four inches of snow shuts down Atlanta and barely slows Buffalo, so the calculator measures tonight’s snow against what is normal where you live: the one-day snowfall your area gets about once a winter, from NOAA and Environment Canada climate normals. In Atlanta that is under half an inch; in Buffalo, about 9½ inches. A snowfall that size, ending overnight, scores about 50%. The National Weather Service thinks the same way: the snow that triggers a Winter Storm Warning in the Northern Plains is “typically much higher” than in the Southeast.
- Ice counts more than snow. Freezing rain glazes roads in a way plows can’t fix and brings down power lines. The NWS usually issues an Ice Storm Warning for “around 1/4 inch or more”. The calculator counts a quarter inch of ice as more than twice your area’s once-a-winter snowfall, so it outweighs 3 inches of snow in most places. Where ice is rare and salt trucks are few, as in Atlanta or Houston, it counts up to 2.4 times more (our judgement).
- Timing. Snow that stops by about 5 AM gives plows time, which makes a delay more likely than a closure. Snow still falling while buses run pushes toward a closure. Snow starting mid-morning means an early dismissal more often than a closure.
- Temperature and wind. Above freezing, snow melts on the roads; below about 15 °F road salt works poorly. Wind over 15 mph drifts snow back across open roads.
- Wind chill. Olentangy, Ohio will consider closing below −15 °F wind chill, metro Detroit districts close around −20 °F, Saint Paul may call an e-learning day at −35 °F or colder, and Duluth closes at a sustained −40 °F. Waterloo Region considers cancelling buses at a −35 °C wind chill; Calgary cancels at −35 °C air or −40 °C wind chill, Winnipeg at −35 °C air or −45 °C wind chill. A forecast that just meets a rule scores about 75%. Where we found no rule, the calculator estimates one: in the published rules, the threshold sits about 45 °F (25 °C) below the area’s average winter low.
- Small nudges: snow days already used (down, though Ontario consortia say they don’t count them for buses) and a Friday or the day before a break (up).
The result is rounded to 5%, with a range for a forecast a third lower or higher. It is a rule of thumb, not your district’s decision.
How schools actually decide
In most US districts the superintendent makes the call before dawn. At Olentangy Schools in Ohio a team starts “around 4 a.m.”, checking temperatures and wind chills and driving assigned areas, and the superintendent decides “between 5:15 and 5:30 a.m.” Most announcements land between 5 and 6 AM, or the evening before.
The calendar matters too. Michigan counts the first 6 days lost to storms as days of instruction, plus up to 3 more with state approval (MCL 388.1701). Pennsylvania allows up to five Flexible Instructional Days, and many districts now switch to an e-learning day instead of a true snow day. Keep track of the days your school has used on a printable school year calendar.
Ontario: buses cancelled, schools open
In Ontario a “snow day” usually means the buses are cancelled while schools stay open. Regional transportation consortia decide by about 6 to 6:30 AM, often by weather zone. York Region’s public board says schools “will remain open unless otherwise stated, even when buses have been cancelled”. Full closures come only with big storms: on January 26, 2026, after a record 46 cm fell at Pearson in one day, most Toronto-area boards closed. Hamilton’s public board is the exception: it closes its schools whenever buses are cancelled for weather. So for Ontario, the headline number is the chance buses are cancelled. Manitoba, Saskatchewan and Alberta work the same way; Quebec, Atlantic Canada and British Columbia close schools.
Where to find the official call
- United States: your district’s website, app or alerts, and your local TV station’s closings list.
- Ontario: your transportation consortium’s cancellations page (the calculator links it for your area) and your board’s website.
- Elsewhere in Canada: your school division, board or school service centre, and local radio.
Got the day off? Settle who shovels the driveway with the wheel spinner, or print a round of snow day bingo with the bingo card generator.
Sources, checked September 2026: NOAA NCEI U.S. Climate Normals 1991–2020; Environment and Climate Change Canada, Canadian Climate Normals 1981–2010; National Weather Service winter alert criteria and wind chill chart; the district and consortium policies linked in the calculator.