Winter tool · US & Canada
Snow Day Calculator
Scores the next school day from the forecast between 7pm and 9am: how much snow falls, whether it is still falling when buses roll, freezing rain, wind chill, and any National Weather Service warning.
An estimate, not a prediction. The only official word is your school or district's announcement.
Next school day
--/ 99estimate
Enter a ZIP code or town to see a score for the next school day, and the one after it when the forecast reaches that far.
An estimate from forecast data, not a prediction of your district's decision. Only your school or district announces closures.
What moved the score
| Factor | Points |
|---|---|
| Snowfall before schoolInches expected from 7pm the night before through 9am. | — |
| TimingWhether snow is still falling when buses run, 5am to 8am. | — |
| Freezing rain and drizzleFreezing rain or drizzle overnight or at commute time. | — |
| Extreme coldLowest feels-like temperature between 5am and 9am. | — |
| Wind and blowing snowGusts and visibility, counted only when there is snow to blow. | — |
| National Weather Service alerts (US)Winter warnings and advisories covering that morning. | — |
| School type (your input)Colleges and private schools close less often. | — |
| How often your district closes (your input)Your read on how easily your district closes. | — |
How the estimate works
Each factor adds points. The total is scaled by your two answers, then held between 0 and 99. The same rules run for every location, and the table below is generated from the code that scores it (snow-day-heuristic-v1).
| Factor | Range | Rule |
|---|---|---|
| Snowfall before school | 0 to 55 | Counts snow from 7pm the evening before through 9am in full (shown as 7pm–6am overnight plus 6am–9am), snow from 6am to 7pm the day before at half weight (it has had time to be cleared) and snow during school hours, 9am–3pm, at 0.3 weight (early-dismissal risk). The result screen lists every part of the sum. About 1 in scores 12, 2 in scores 22, 4 in scores 35, and 8 in or more reaches the 55 cap. |
| Timing | -5 to +8 | +8 if snow is still falling during the 5am to 8am window when buses run. -5 if light-to-moderate snow (under 3 in) ends by 3am, leaving plows time. Needs hourly data, so it only applies within about 48 hours. |
| Freezing rain and drizzle | 0 to 25 | Freezing rain overnight or at commute time: +18 for one hour, +25 for two or more. Freezing drizzle only: +10. From the daily outlook: +18 or +8. |
| Extreme cold | 0 to 25 | Lowest feels-like temperature between 5am and 9am: -5°F or colder +6, -15°F or colder +15, -25°F or colder +25. Districts set their own wind-chill thresholds, so treat this as a rough signal. |
| Wind and blowing snow | 0 to 15 | Only when snow is falling or at least 0.5 in is expected: gusts of 35 mph +8, 45 mph +12, plus +3 if visibility drops under 0.3 mi (0.5 km). |
| National Weather Service alerts (US) | 0 to 30 | Highest active alert covering that morning: Blizzard or Ice Storm Warning +30, Winter Storm Warning +25, Extreme Cold or Wind Chill Warning +20, Winter Weather Advisory +10, Winter Storm Watch +8, Cold Weather or Wind Chill Advisory +6. Only the single highest counts. |
| School type (your input) | ×0.6 to ×1 | Public ×1. Private ×0.9. College ×0.6, since residential campuses rarely close for snow alone. |
| How often your district closes (your input) | ×0.75 to ×1.2 | Rarely ×0.75, sometimes or not sure ×1, often ×1.2. This is how the estimate accounts for local snow tolerance: a district in Buffalo and one in Atlanta react very differently to the same 3 inches. |
Snow day questions
- How accurate is this snow day calculator?
- There is no accuracy figure to give you, and we would be wary of any snow day predictor that quotes one. No public dataset records which districts closed on which days, so this calculator cannot be tested against real decisions. It is a transparent scoring of the forecast: every point comes from a factor listed on this page. Read the score as a measure of how rough the morning looks, not as odds.
- How much snow does it take to cancel school?
- It depends far more on where you live than on any fixed number. A district that sees little snow may close for an inch or two, or for a glaze of ice, while districts used to heavy winters often stay open with half a foot on the ground. That is why the calculator asks how often your district closes: it is the best local signal available without closure records.
- Why is ice weighted so heavily?
- Freezing rain coats roads, sidewalks and bus stops in a way plows cannot push aside, and a thin glaze can be more dangerous for buses than several inches of snow. The calculator adds up to 25 points for freezing rain or drizzle overnight or at commute time, even when no snow is forecast.
- Does it work in Canada?
- Yes, for any town or city with a forecast. Search Canadian locations by name rather than postal code. Official alerts are only checked for US locations, through the National Weather Service, so Canadian results do not include Environment and Climate Change Canada warnings.
- Does it know about holidays or teacher workdays?
- No. It skips Saturdays and Sundays to find the next school day, but it has no school calendar. If tomorrow is already a day off, the score does not matter.
- Why does the score stop at 99?
- Because no forecast makes a closure certain. Even with a blizzard warning in effect, the decision belongs to your district, and some stay open or switch to a remote day instead.