Snow day calculator: will school be closed tomorrow?
Enter your ZIP code. The calculator reads the National Weather Service forecast for the night before school – snow, ice and wind chill – and weighs it against how much it takes to close schools where you live.
Why this for Lewiston
- no measurable snow forecast overnight
- wind chill down to 33°F before school
- Lewiston is in the snow belt, where it takes 6 inches or more – or extreme cold – to close schools
Snow and ice in the week ahead
| Day | Snow | Ice | Low |
|---|---|---|---|
| Fri Oct 16 | – | – | 33°F |
| Sat Oct 17 | – | – | 25°F |
| Sun Oct 18 | – | – | 25°F |
| Mon Oct 19 | – | – | 30°F |
| Tue Oct 20 | – | – | 32°F |
| Wed Oct 21 | – | – | 32°F |
| Thu Oct 22 | – | – | 32°F |
NWS forecast office GYX. Updated hourly.
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Snow day chances by state
How the chance is calculated
The night that matters. Superintendents decide early in the morning, so the calculator adds up the snow and ice forecast between 6 PM and 8 AM before the school day, and the coldest wind chill between 5 and 8 AM, when children walk or wait for buses.
What your area is used to. The same storm means different things in Atlanta and in Buffalo. The calculator uses three levels: in the South about 1.5 inches of snow (or a glaze of ice) gives an even chance; in the middle band – Virginia to Missouri, the Ohio Valley, the Pacific Northwest – about 4 inches; in the snow belt from Minnesota to Maine about 6.5 inches, or wind chills around −25 °F.
Ice counts more than snow. A tenth of an inch of freezing rain coats roads and brings down branches and power lines; the calculator treats about 0.15 inch of ice like a full closing-level snowfall. Very cold air pushes the chance up too, because snow at 15 °F stays on roads that salt cannot clear.
The curve. These pieces become one score – 1 means the storm is right at your local closing level – and a smooth curve turns it into a percentage: around 50 % at the level, above 80 % at one and a half times it, under 10 % at half of it.
Snow day questions
How does the snow day calculator work?
It reads the National Weather Service forecast for your ZIP code – how much snow and ice is expected between 6 PM and 8 AM, and how cold the wind chill gets before school – and compares it with what it takes to close schools where you live: about an inch of snow or any ice in the South, 3–5 inches in the middle of the country, 6 inches or more (or extreme cold) in the snow belt. The bigger the storm relative to that local level, the higher the chance.
How accurate is it?
As accurate as the forecast and as predictable as your district. Snow forecasts the evening before are usually within an inch or two; ice and the timing of a storm are harder. Districts also weigh things the forecast cannot see – bus routes on hills, whether plows can finish by 6 AM, how many days they have already used. Treat 50 % as a coin toss and check again at night and early in the morning.
What makes schools close besides snow?
Ice is the most common reason in the South and the Mid-Atlantic: a tenth of an inch of freezing rain makes roads more dangerous than several inches of snow. In the northern plains and the Upper Midwest, dangerous wind chills (often −25 to −35 °F) close schools even without snow, because children wait for buses outside.
When do districts announce a snow day?
Most decide between 4:30 and 6 AM after checking the roads, some the evening before when a big storm is certain. Announcements go out by text, e-mail, the district website and local TV.
Why is my chance low when it is snowing a lot?
Snow that falls during the school day does not count for the morning decision, and snow ending in the evening gives plows the night to clear roads. The calculator only counts snow and ice from 6 PM to 8 AM; a delayed start (two-hour delay) is more likely than a full closing when the total is near the local level.
More
Forecast: National Weather Service gridded forecast (api.weather.gov) – snowfall, ice accumulation, temperature and wind chill. ZIP codes: GeoNames (CC BY 4.0). The chance is 77.today's estimate from the forecast and local snow tolerance; only your school district decides. Not affiliated with any school or district.