Manual Snow Day Calculator
Enter the storm. See the chance school closes.
Type in the snow, ice and cold you expect. The result uses the same model as our snow day calculator, which reads the National Weather Service forecast for you.
Your storm
An estimate from the numbers you entered, not a decision. Your school district decides. For tonight's real forecast, use the snow day calculator.
How the manual calculator works
Each hazard is measured against your area's own line. Snow is compared with the overnight total that usually closes schools where you live, ice with a small threshold that barely changes by region, and wind chill with a cold line from your normal winter low. The biggest hazard counts in full and the others add a third of their weight, so a snow-and-ice storm scores higher than either alone. An NWS warning raises the chance. The full method has the numbers.
Try a few versions of the same storm: 4 inches overnight versus 4 inches after 8 AM, or the same snow with a tenth of an inch of ice on top. Timing and ice move the result more than most people expect.
Manual calculator questions
How is this different from the snow day calculator?
The snow day calculator reads tonight's National Weather Service forecast for your ZIP code. This manual version uses the numbers you type in, so you can test a storm before it is in the forecast, compare 3 inches with 6, or see how much ice changes the answer. Both use the same model.
Why does my ZIP code change the result?
The same storm means different things in different places. The calculator sets a local snow line from how often your area gets 3 or more inches of snow in a day (NOAA 1991–2020 normals) and a cold line from your normal winter low. Without a ZIP it uses the climate you pick.
Should I count snow that falls during the school day?
Yes, in its own box. Snow that starts after buses run is more likely to cause an early dismissal than a closure, so the model gives it less weight than snow that falls overnight.
What do the school and district settings do?
They nudge the result: colleges close less often than K–12 schools, private schools a little more often, and some districts are known for closing early or for staying open. They are rough adjustments, not measured from data yet.