Snow Day Calculator
Will school close tomorrow? Enter your ZIP code for an estimate built from the National Weather Service forecast for your area, with every number shown.
Chance of a snow day
Enter your ZIP code
The estimate covers the next two school days (Monday to Friday).
How this is calculated
The calculator asks the National Weather Service for the hour-by-hour forecast at the center of your ZIP code. For each of the next two school days it adds up the snow and ice forecast for the window from 6 PM the evening before to 10 AM that morning, when districts decide and buses run.
Ice counts twelve times as much as snow, because a thin glaze stops traffic faster than a few inches of powder: a quarter inch of ice counts like 3 inches of snow. The National Weather Service usually issues an Ice Storm Warning at around a quarter inch.
How much it takes to close school depends on where you live. The Weather Service notes that the snow amount behind a Winter Storm Warning in the Northern Plains is much higher than in the Southeast. So the calculator lets you say how often your district closes, and sets the amount at which the chance reaches 50%:
| District closes | Snow and ice (inches) |
|---|---|
| Rarely | 1 |
| Sometimes | 3 |
| Often | 6 |
Around that point the chance rises along an S-curve: with “sometimes”, 2 inches give about 25% and 4 inches about 75%. Points are then added for dangerous cold at bus time and for active winter alerts from the Weather Service, and taken off when a district has already used several snow days, for private schools, and more for colleges.
| Alert | Points |
|---|---|
| Blizzard Warning | 25 |
| Ice Storm Warning | 25 |
| Winter Storm Warning | 15 |
| Extreme Cold Warning | 15 |
| Wind Chill Warning | 10 |
| Winter Weather Advisory | 5 |
| Cold Weather Advisory | 3 |
| Wind Chill Advisory | 3 |
These thresholds and points are our rule of thumb, set by hand. They are not a statistical model fitted to closing records, and no district uses them. Treat the result as a way to read the forecast, not a prediction of what your superintendent will decide.
Sources
Checked against the sources below on .
Questions people ask
How accurate is a snow day calculator?
It can only be as good as the forecast and the rule behind it. This one uses the National Weather Service forecast for your area and shows exactly how it turns snow, ice and cold into a percentage. Forecasts change, so check again the evening before and in the morning.
Who decides whether school is closed?
Your school district, usually the superintendent, together with transportation staff who check the roads. Closings are announced on the district's own website, app, phone alerts and local news. A calculator can't know that decision.
Why does ice count more than snow?
Freezing rain coats roads, sidewalks and power lines in a layer that plows can't push away. The National Weather Service usually issues an Ice Storm Warning at around a quarter inch of ice, while the same depth of snow would barely matter in most places.
Why does my state change the result?
Districts that see little snow close for less. We start from a setting for your state and you can change it: "rarely" puts the 50% point at 1 inch, "sometimes" at 3 inches and "often" at 6 inches.
Does it work for a delay instead of a closing?
Not directly. A two-hour delay often comes with smaller amounts or with snow ending before morning. If the chance shows as possible, a delay is worth watching for.