Thresholds by region
How Much Snow Cancels School?
There is no single number, and here is why.
The honest answer depends on where you are, when the snow falls, and whether any of it is ice. All three are below, with working numbers in inches and centimetres.
The Short Answer
Across the United States, five to six inches of overnight snow is the most common closure trigger. Across Canada it is roughly 15 to 25 centimetres, though buses are usually cancelled well before schools close. In the UK and Ireland, 3 to 8 centimetres can be enough.
Those figures are almost useless on their own, though, because the variation around them is larger than the numbers themselves. Two inches closes schools in Georgia. Ten inches does not close them in northern Minnesota. What follows is the version worth actually using.
| Region | Typical trigger | Why |
|---|---|---|
| Southern US | 1–2 in / 3–5 cm | Very few plows, no salt routine, drivers with no winter experience. Snow is an emergency rather than a season. |
| Mid-Atlantic | 3–4 in / 8–10 cm | Some equipment, but hilly terrain and heavy bus reliance. |
| Midwest & Northeast US | 5–6 in / 13–15 cm | Well equipped and used to it. The classic snow-day threshold. |
| Northern Plains, Upper Midwest | 8–12 in / 20–30 cm | Extensive fleets and high tolerance. Cold closes schools here more often than snow does. |
| Mountain West | 8–12 in / 20–30 cm | Snow is routine; road grade and avalanche control matter more than depth. |
| Canada | 15–25 cm | Buses are usually cancelled first while schools stay open. A true closure needs a lot. |
| UK & Ireland | 3–8 cm | Very little equipment, and staff being unable to travel closes as many schools as the roads do. |
Even within one state the split can be large: Michigan is the clearest example, where west-side lake-effect districts hold open through amounts that close the eastern side of the same state.
Want the number for your own district rather than your region? The snow day calculator applies these thresholds to your actual forecast, and the two-hour delay calculator covers the outcome that is more likely than a closure on a borderline morning.
Timing Beats Total
If you remember one thing from this page, make it this: when the snow falls matters more than how much falls.
Six inches that finishes at 10pm gives road crews the entire night on empty roads. By 6am the routes are clear and school opens normally. Three inches still falling at 6am closes the district, because the plows are losing ground at exactly the moment buses need to move and the 5am road patrol can see that they are.
The critical window is roughly 3am to 8am. Snow inside it is worth several times its depth in closure odds. This is why two towns given identical 24-hour totals can get opposite decisions, and why a forecast that only tells you a daily total cannot answer the question.
Ice Changes the Numbers Entirely
Every figure on this page is for snow. Freezing rain works on a different scale:
| Ice accumulation | Effect |
|---|---|
| 0.10 in / 2.5 mm | Roads and sidewalks genuinely dangerous. Closures widespread — more disruptive than six inches of snow. |
| 0.25 in / 6 mm | Tree limbs and power lines start coming down. Closures near-certain, sometimes for several days. |
| 0.50 in / 12 mm | Major infrastructure damage and prolonged power outages. |
A tenth of an inch of ice beats eight inches of powder. If freezing rain is in the forecast, stop reading snow thresholds.
What Else Moves the Threshold
- Wind. Loose snow with gusts over 30 mph drifts back across roads crews just cleared. Five inches with wind closes more districts than ten inches without it.
- Cold. Below about 15°F salt stops working, so the same snowfall is harder to clear. Extreme cold also closes schools with no snow at all.
- Snow days already used. A district that has spent its allowance pushes hard to stay open, because every further closure extends the school year.
- How students travel. A district where most children walk faces an ice-and-sidewalk problem. A district that buses everyone faces a rural-road problem.
- Remote learning. Districts set up for e-learning convert closures into remote days, which raises their apparent snow threshold without changing their judgement.
Common Questions
How many inches of snow does it take to cancel school?
There is no national number. In the southern US, one to two inches is often enough. Across the Midwest and Northeast, five to six inches is a common trigger. In genuinely snowy places schools frequently run normal days on eight inches or more. Timing matters as much as the total: three inches falling during the morning commute closes more districts than eight inches that ends at midnight.
How many centimetres of snow cancels school in Canada?
Roughly 15 to 25 cm overnight puts a closure in play across most of Canada, but the far more common outcome at those amounts is that buses are cancelled while schools stay open. In the UK and Ireland, 3 to 8 cm can be enough to close schools outright.
Does the timing of the snow matter more than the amount?
Often, yes. Snow falling between roughly 3am and 8am counts for several times its depth, because that is when the closure decision gets made and crews have run out of time. Six inches that finishes by 10pm is a plowed road by 6am; three inches still falling at 6am is a closure.
How much ice does it take to cancel school?
Far less than snow. A tenth of an inch of freezing rain is more dangerous than eight inches of powder, because it defeats plows, coats sidewalks and bus steps, and brings down power lines. Any forecast of freezing rain should be read as a much higher closure risk than the precipitation total suggests.
Why does the same snowfall close one district and not the next?
Plow capacity per road mile, how many students walk versus ride, hill grades, how many snow days the district has already spent, and whether it has a remote-learning option. These vary enormously between neighbouring boards and explain most disagreements on identical forecasts.
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.