Wind chill · No snow required
Cold Day Calculator
Will school close for extreme cold?
Some of the coldest school closings of the year happen on clear, dry mornings. This scores wind chill rather than snowfall, because that is what a cold-day policy actually measures.
Cold-Day Closure Chance
Snow in the forecast too? The snow day calculator scores the whole picture.
A Cold Day Is a Different Decision
Almost every snow day calculator treats cold as a modifier on snowfall. That gets the logic backwards for a whole category of closures, because a cold day is not a road problem at all.
When a district closes for snow, the question is whether buses can safely drive the routes. When it closes for cold, the roads are usually perfect — often dry and sunny. The question is whether a child standing at an unsheltered stop, possibly for fifteen minutes if the bus runs late, is at risk of frostbite. Those are different questions with different answers, which is why this page scores wind chill at 78% of the total and leaves snow out of it.
Why Wind Chill and Not Temperature
Districts write their policies in wind chill because that is what determines injury. Air at −10°F with a 25 mph wind strips heat from exposed skin about as fast as still air at −35°F. A policy written in plain temperature would let dangerous mornings through and close on harmless ones.
| Wind chill | Frostbite risk on exposed skin | Typical district response |
|---|---|---|
| 0°F / −18°C | Low with normal winter clothing | Normal day |
| −15°F / −26°C | About 30 minutes | Warnings to families; some southern districts delay |
| −20°F / −29°C | About 30 minutes | Delays common; closures in milder regions |
| −25°F / −32°C | 10 to 30 minutes | Buses often pulled; closures widespread |
| −35°F / −37°C | Roughly 10 minutes | Closure in most districts that see this at all |
| −50°F / −46°C | Under 5 minutes | Closure essentially everywhere |
Those windows are the point. A bus running fifteen minutes late is an ordinary event; at −35°F it stops being ordinary.
The Threshold Moves with the Region
Cold-day policies vary more between districts than snow policies do, because they are written against local norms rather than against physics.
- Northern Plains, northern Ontario, the Prairies. Cutoffs around −35°C to −40°C wind chill. Families own the clothing, stops are planned for it, and −25°C is an ordinary Tuesday.
- Great Lakes and New England. Commonly −20°F to −25°F. Cold enough to be rare, frequent enough to have a written policy.
- Mid-Atlantic and the southern US. Often no written cold policy at all. When genuine cold arrives it closes schools at temperatures a northern board would ignore, because nothing is set up for it.
- UK and Ireland. Cold almost never closes schools on its own; ice and snow do the work instead.
Set the regional control in the form to match where you actually are — it moves the result substantially, and it is the main reason two towns get different answers to the same forecast.
Cold Day Questions
How cold does it have to be to cancel school?
There is no single national figure, but most districts that have a written cold policy sit somewhere between -20F and -35F wind chill, and many Canadian boards use -35C to -40C. The decision is about children waiting at unsheltered bus stops rather than about whether roads can be driven.
Do schools close for cold with no snow at all?
Yes, routinely. A clear, dry, brilliantly sunny morning at -30F closes more schools in the northern US and Canada than a moderate snowfall does. The calculator on this page ignores snow almost entirely and scores wind chill.
What is the difference between temperature and wind chill?
Temperature is what a thermometer reads. Wind chill is how fast exposed skin actually loses heat once wind is factored in, and it is the number districts use, because it is what determines frostbite risk at a bus stop. At -10F with a 25 mph wind, the wind chill is closer to -35F.
How quickly can frostbite happen?
At about -30F wind chill, exposed skin can be frostbitten in roughly 10 to 30 minutes. At -50F it can take under 5 minutes. Those windows are shorter than a child may wait for a late bus, which is the entire reason cold-day policies exist.
Why do northern districts stay open in cold that would close a southern one?
Because their threshold is genuinely lower, and their families are equipped for it. A district in northern Minnesota or northern Ontario expects -30C several times a winter and plans around it. A district that sees it once a decade has neither the clothing norms nor the sheltered stops to handle it.
Are buses cancelled for cold before schools close?
Usually, yes. Transportation is pulled at a milder threshold than the one that closes the building, because the exposure risk is at the stop rather than in the school. The bus cancellation predictor handles that case specifically.
One Important Caveat
This is an estimate for planning, not an official notice. Only your school district can close a school or call a delay. Always check their website, phone system or social media before assuming anything — and never make a travel decision based on this page instead of an official weather warning.