How Our Snow Day Calculator Works
The Snow Day Calculator gives a statistical estimate of the chance that schools in your area close for the day, based on live forecast data. It is not an official announcement — always confirm with your school district.
The scoring model
The tool converts live forecast data into a 0–100 score using a set of transparent factors. Each factor contributes points based on the latest forecast, and the total is mapped to a percentage chance of a snow day.
Scoring factors
| Factor | Points |
|---|---|
| Expected snowfall in next 24h | Up to 55 pts: ≥20 cm = 55, 12–20 cm = 40, 7–12 cm = 28, 3–7 cm = 16, 1–3 cm = 8 |
| Overnight timing bonus | +40% of snow points when snow falls between 10pm and 7am (morning commute impact) |
| Extreme cold | Up to +20: ≤ −20°C = 20, ≤ −15°C = 12, ≤ −10°C = 6 |
| Ice risk | +12 when rain is likely (≥50%) and temperature is near freezing (−3°C to 2°C) |
| High winds with snow | +8 at ≥60 km/h |
| High snow-flurry chance | +6 when snow chance is ≥70%, even with little accumulation |
What the percentage means
- Under 20%: Very unlikely
- 20–40%: Unlikely
- 40–60%: Possible
- 60–80%: Likely
- 80% and above: Very likely
The score is capped between 3% and 97% — never 0% or 100% — because weather is inherently uncertain.
Data source
The calculator uses live forecast data from WeatherAPI.com, fetched fresh on every search: current conditions plus a 2-day outlook.
Limitations
These are estimates only. School districts make the real call based on road crews, buses, and local policy. Snow days also depend on local differences — a few centimeters can shut down a rural district while barely affecting a big city — and forecasts can change quickly.
How Reliable Is the Prediction?
Predictions checked 6–12 hours before school starts are generally more reliable than ones checked two days out, because weather forecasts sharpen considerably as the event approaches. A score generated late at night or in the early morning reflects much fresher data than one produced 48 hours earlier. Keep in mind that this tool produces a statistical estimate from forecast data — not official district information — so always confirm with your school district.
Scoring in Plain English
Put simply: the expected amount of snow carries the most weight in the score. Snow falling overnight boosts the score further, since it disrupts the morning commute. Extreme cold and ice risk add additional points. The final number is capped between 3% and 97% — the tool never claims absolute certainty.
Snow Day vs 2-Hour Delay vs Early Dismissal — What Your Score Means
Schools have four possible responses to winter weather: a full closure (snow day), a 2-hour delayed start, an early dismissal, or opening on a normal schedule. Here is how the tool’s percentage bands map to those outcomes:
- 80%+ — Full closure likely.
- 60–79% — Closure possible, 2-hour delay very likely.
- 40–59% — 2-hour delay likely.
- 20–39% — Delay possible.
- Below 20% — School on time very likely.
Only your school district decides — this is a statistical estimate, not an official announcement.
When to Check for School Closures
- Check 7–10 PM the night before for an early read on tomorrow.
- Check again 4:30–6:00 AM — this is when districts usually make the final call.
- Snow falling between 3–7 AM affects morning bus routes the most.
- Snowfall timing and rate matter more than the total inches.