No public snow day calculator can promise a universal accuracy percentage without a complete, verifiable history of forecasts and decisions for every district it serves. This site does not make that claim.
What the estimate uses
The model uses live forecast snowfall, possible icing, minimum and maximum temperature, wind, precipitation probability and snowfall timing. User-selected area, school and district-tendency settings add broad context. Review the exact factor weights and thresholds.
For supported U.S. locations, active National Weather Service winter alerts are displayed as separate official context. They do not change the percentage because the six-factor model has not been calibrated to use alert status as an additional weight.
What the estimate does not know
- real-time conditions on every district road and bus route;
- pavement treatment, plow progress or crash response;
- staff and bus-driver availability;
- building power, water, heat or access problems;
- the district's final policy and human judgment.
Why results can change
Forecast providers update model guidance as observations arrive. Snow bands can shift, precipitation can change type and the heaviest period can move into or away from the school commute. The full accuracy guide explains why changing with the forecast is expected behavior.
Not safety or emergency advice
Do not use the calculator to decide whether a road is safe, whether to ignore a warning or whether emergency travel is appropriate. Even when an NWS alert is shown beside a result, follow the linked official forecast, emergency management and transportation authorities. Learn how to distinguish those notices in the winter weather alert guide.
Not an official school notice
Only a school district or authorized school official can announce a closure, delay, early dismissal, bus cancellation or remote-learning day. The model estimates broad closure pressure and may not match the district's response.
Why no accuracy percentage appears anywhere on this site
A published accuracy figure would need a verified record of what this model predicted and what every covered district actually decided, matched day by day across many winters and thousands of school systems. No such dataset exists here, and building one would mean collecting closure decisions from every district on the site. Until that exists, any percentage would be a marketing number rather than a measurement, so none is offered.
The same reasoning rules out ranking this calculator against others. You will not find a “most accurate” claim on this site, because there is no evidence that would support one. What is offered instead is inspectability: every threshold is published, every forecast value is shown, and who built it is stated openly.
Forecast inputs change, so the estimate changes
The weather data itself is revised as new observations arrive, typically several times a day. A storm track can shift, a rain-snow boundary can move by thirty miles, and the heaviest period can slide into or out of the morning bus window. When the estimate moves overnight, it is because the forecast underneath it moved. A tool whose number never changed would be ignoring new information, not being more reliable.
School district decisions vary, even under identical weather
Two neighbouring systems facing the same storm can reach different conclusions, and both can be right for their own circumstances. Route length, terrain, equipment, driver availability, building condition, the number of closure days already used, and local expectations all feed into a judgement that no weather model observes. In much of Canada the usual outcome is a transportation cancellation rather than a closure at all, which is covered on the Canada page.
Predictions do not replace official closure announcements
This is the one rule with no exceptions. An estimate on this site is never an announcement, a forecast of an announcement, or a reason to act as though an announcement has been made. Only the school, district, board, division or service centre responsible for a building can declare a closure, delay, transportation cancellation, early dismissal or remote-learning day, and only its own message confirms which of those applies.
Where to check official information instead
- United States weather: the National Weather Service for forecasts and active warnings, and its winter safety guidance.
- Canadian weather: Environment and Climate Change Canada public alerts.
- Road conditions: the state or provincial travel service linked on each city and regional page.
- School status: your district, board, division or service centre, and in much of Ontario the regional student transportation consortium.
Proper use: use the estimate to prepare a backup plan, refresh as the event approaches, and confirm every final decision with the district.
For a practical routine, follow the best times to check and the family preparation checklist.
This statement was last reviewed on .