Snow Day Calculator.
Estimate whether wintry weather could disrupt the next school day. Enter a US ZIP code, Canadian postal code or UK postcode to check overnight and morning snow, sleet, temperature and wind from live forecast data.
Snow day chance
Choose a country and enter a ZIP or postal code to check the next school-day weather risk.
Forecast data: MET Norway. Location lookup: Zippopotam.us / GeoNames. This is a weather-based estimate, not an official closure forecast. US locations use ZIP-code centroids; Canadian locations use FSA areas and UK locations use postcode districts, so local conditions can differ within the lookup area.
How the snow day estimate works
The calculator checks the forecast from 6:00 PM on the evening before the next weekday through 10:00 AM on the school day. It looks for forecast periods marked as snow or sleet, how long those conditions last, whether they continue into the morning, the lowest temperature and the strongest wind.
Those weather factors are combined into a transparent 0–95 weather-risk score. The score is intentionally capped below 100 because a weather forecast cannot know a district's final decision, road treatment, bus-route conditions, staffing, local policy or last-minute changes.
Why this is not an exact school-closure probability
There is no universal snowfall threshold that closes every school. Two districts with the same forecast can make different decisions because terrain, road networks, plowing capacity and local policies differ. The optional school-tendency control makes only a small adjustment and does not pretend to model a district's private decision process.
Forecast data also changes as a storm approaches. Check again closer to the school morning and always use your school, district or local authority as the final source for closure and delay announcements.
Location and forecast data
Postal-code lookup is performed on the server and converted to an approximate latitude and longitude. The weather provider receives those coordinates rather than the ZIP or postal code you entered. Forecast responses are cached to reduce unnecessary upstream requests.
Canada's open postal dataset is available at Forward Sortation Area level (the first three characters), and the UK lookup used here is at postcode-district level. That is useful for a regional snow-day estimate but should not be treated as street-level weather data.
Forecast & location data sources
The calculation uses public forecast and postal-area data. Links below document the upstream services, licensing and usage requirements.
Frequently asked questions
Is the Snow Day Calculator an official school closure forecast?
No. It is an independent weather-based estimate. Your school, school district or local authority makes the official closure or delay decision.
What countries does the calculator support?
The current version supports the United States, Canada and the United Kingdom. US lookup uses a 5-digit ZIP code, Canada uses the first three postal-code characters (FSA), and the UK uses the postcode district.
Does the percentage mean it is statistically 70% certain my school will close?
No. The percentage is a transparent weather-risk score based on forecast snow or sleet, timing, temperature and wind. It is not a calibrated historical probability for your individual school.
Why can the result change later?
Weather forecasts are updated as new observations and model runs arrive. Storm track, precipitation type, timing and temperature can all change, so the estimate may change when you check again.
Does the calculator know school holidays or teacher workdays?
No. It skips weekends when choosing the next weekday, but it does not know individual school calendars, holidays, remote-learning policies or scheduled closures.