Ontario · In centimetres · Free
Snow Day Predictor Ontario
Will school be closed tomorrow?
Pick your city below or type it in. Built for how Ontario actually works — in centimetres, with snow squalls and the bus-versus-school split that catches families out every winter.
Your Closure Chance
In Ontario the more likely outcome is a bus cancellation, not a closure — check the bus cancellation predictor for that.
Check Your Ontario City
Tap a city to run it through the predictor. Grouped by the thing that actually decides your winter: which weather system you sit under.
Snowbelt — Georgian Bay and Lake Huron Squalls
The subtitle is the region or board area, which is usually what determines your bus zone.
In Ontario, the Buses Go First
This is the single most important thing to understand about Ontario winters, and it catches families out every year. You check whether school is closed, see that it is open, put your child at the end of the driveway — and no bus ever comes.
Ontario boards rarely close schools. What happens instead is that the student transportation consortium cancels buses while the building stays open for anyone who can get there. The two calls are made by two different organisations, on different criteria, and announced separately.
So on a typical bad Ontario morning the honest answer is: no bus, but school is running. If you are really asking whether a bus will show up, the bus cancellation predictor is the tool you want — it weighs blowing snow and open concession roads far more heavily, because that is what actually pulls buses off the road.
Your Consortium, Not Your Board
Transportation is run by consortia that serve several boards at once, and they split their territory into zones. It is completely normal for the rural north of a zone to lose its buses while the urban south runs a perfectly ordinary morning. Find your zone once at the start of winter and every subsequent announcement becomes easy to read.
Why Snow Squalls Close Your Town and Not the Next One
Most of Ontario's disruptive snow is not from big system storms. It is lake effect — narrow squall bands coming off Georgian Bay, Lake Huron and Lake Ontario when cold air crosses open water.
Squalls behave nothing like a normal snowfall. A band can sit over one town and dump 20 cm in a few hours while a community twenty kilometres away sees blue sky. They set up and collapse quickly, and they produce sudden whiteouts on exactly the open rural roads buses use.
This is why Barrie, Collingwood and Owen Sound cancel buses on mornings when Toronto is completely clear, and why a provincial forecast tells you very little about your own driveway. It is also the main reason a snow day predictor has to work from your specific coordinates rather than a regional average.
| Region | What drives closures there |
|---|---|
| Simcoe, Grey, Bruce | Georgian Bay squalls. Highly localized, high totals, frequent bus cancellations even in a well-equipped board. |
| Northern Ontario | Extreme cold as much as snow. Buses come off at roughly −35°C to −40°C wind chill with no snow at all. |
| GTA and Peel/York/Durham | System storms and freezing rain. Dense plow coverage, so closures need a genuinely large event. |
| Waterloo, Wellington, Brant | Mixed. Squalls off Huron reach here weakened, but freezing rain is common and decisive. |
| Southwestern Ontario | Lake Huron and Erie squalls plus ice storms. Windsor and Chatham see less snow but more freezing rain. |
| Eastern Ontario and Ottawa | Big system snowfalls and deep cold. High tolerance — Ottawa runs on amounts that would close a southwestern board. |
How Much Snow Closes School in Ontario?
Less usefully than people hope, because accumulation is rarely the deciding factor. These are working ranges, in centimetres, for the overnight period before a school morning.
| Overnight snow | Typical Ontario outcome |
|---|---|
| Under 5 cm | Nothing happens, unless it comes with freezing rain or heavy blowing snow. |
| 5–10 cm | Rural bus cancellations are realistic, especially with wind. Schools open. |
| 10–15 cm | Widespread bus cancellations likely. Schools still usually open. |
| 15–25 cm | Buses cancelled almost everywhere affected; a closure becomes genuinely possible. |
| Over 25 cm | Closure likely, particularly if it is still falling through the morning. |
| Any freezing rain | Skip the table. Ice defeats plows and gravel roads cannot be salted — this is the strongest single trigger in Ontario. |
Two things move the answer more than the number in that table. Timing: snow still falling between 3am and 8am is worth several times its depth, because the pre-dawn road patrol is what the decision is built on. Wind: 5 cm of loose snow with 40 km/h gusts drifts across open concession roads and closes routes that 15 cm of calm snow would not.
Ontario Snow Day Questions
How much snow closes schools in Ontario?
Ontario boards rarely close schools for snow alone. Roughly 15 to 25 cm overnight puts a closure in play, but the far more common outcome at those amounts is that buses are cancelled while the schools stay open. Blowing snow and freezing rain move the decision more than raw accumulation does.
Why are Ontario buses cancelled but schools stay open?
They are two separate decisions. Student transportation consortia decide whether buses can safely run the routes; the school board decides whether the building opens. Ontario boards keep buildings open so students who can get there safely still have school, and because a closure has to be made up later while a cancelled bus route does not.
What is a snow squall and why does it matter in Ontario?
Snow squalls are narrow bands of intense lake-effect snow coming off Georgian Bay, Lake Huron and Lake Ontario. They can drop 20 cm on one town while the town twenty kilometres away sees nothing, and they produce sudden whiteouts. This is why Barrie, Owen Sound and Collingwood cancel buses on days when Toronto is completely clear.
How cold does it have to be to cancel buses in Ontario?
Most Ontario consortia pull buses when wind chill reaches roughly −35°C to −40°C, with no snow required at all. Children waiting at unsheltered rural stops are the reason, along with the risk of a bus breaking down in dangerous cold.
What time are Ontario cancellations announced?
Transportation consortia patrol the roads before dawn and usually post between 5:30am and 6:30am. Boards announce closures in the same window. If nothing has appeared by about 6:30am, buses are running and school is open.
Can only some bus zones be cancelled?
Yes, and it is normal. Consortia split their territory into zones and frequently cancel the rural north of a board while the urban south runs as usual. Find which zone your route falls in rather than assuming one decision covers the whole board.
Does this work in centimetres?
Yes. Ontario pages default to metric, so snowfall shows in centimetres, temperature in Celsius and wind in kilometres per hour. Switch to imperial in the form if you prefer.
Will it be a snow day tomorrow in Ontario?
Set the day to Tomorrow above and pick your city — tomorrow is the most reliable day to forecast, so the number means something. The snow day tomorrow page covers the same question in more depth, and today has its own page for mornings when the decision may already have been made.
One Important Caveat
This is an estimate for planning, not an official notice. Only your board can close a school and only your transportation consortium can cancel buses. Always check their websites or local radio before assuming anything — and never make a travel decision based on this page instead of an Environment Canada warning.