How much snow does it take for a snow day in Canada?

There is no Canadian centimetre line. A number that closed Vancouver would be a Tuesday in Quebec City, and a number that closed Quebec City might be a nuisance in a Georgian Bay snow belt that has the plows and the habit. Boards do not publish a national chart, and the ones that mention conditions usually talk about safety, timing, and buses rather than a single depth.

What the forecast total hides

The daily snowfall on a weather app is not the number that matters. The number that matters is how much falls in the window between the previous evening and the morning bell, and whether it is still falling when routes start. Ten centimetres spread from 7 p.m. to midnight can be plowed before dawn. Three centimetres that arrive at 6 a.m., on top of ice, can cancel buses. Our curve uses that overnight and early-morning window, then adds a timing bump if the heaviest hour is between 5 and 7 a.m., and eases the score if the snow peaked the evening before and the commute hours look mostly clear.

Ice and cold can produce a high score with almost no snow at all. If you only watch the snowfall field, you will miss those mornings. The freezing-rain guide is the companion piece: ice days and freezing rain.

How the same snow is weighted

The methodology page draws the curve from the same constants the code uses, so this article will not quote a table that can drift. The shape, in plain language, is gentle under a couple of centimetres, steeper through the 5 to 15 cm range where decisions actually vary, and flatter again once the total is already severe. A multiplier then moves the snow points:

• Places saved as low tolerance, notably Vancouver and the south-coast box around it, weigh snow more heavily.
• Places saved as high tolerance, including Barrie, the London–Kitchener side of Ontario, Quebec City, and several northern and Atlantic cities, weigh snow more lightly.
• Everyone else sits on the typical curve.

The multiplier does not touch ice, and it does not touch the cold points used for Prairie and northern wind chill. School type and rural routes are added after that. The published number is capped at 97.

A worked example, from the code

On the methodology page, a 10 cm overnight fall in a typical region, with no ice, no extreme wind, and no pre-dawn burst, is calculated by the live scoring function. Read that figure there rather than memorizing it from an article. If we change the curve, that page changes with it. Your board can still disagree, and it is allowed to. The centimetres were never the decision. They were the input.