Why This Matters for Families and Commuters
Every winter morning that Environment Canada issues a significant snowfall warning, the same questions start circulating in Ontario family group chats: Is school cancelled? Are buses running? Should I book backup childcare?
Those questions have real logistical weight. For parents who rely on bus transportation, a last-minute cancellation at 6:15 AM can mean scrambling for childcare or losing a morning of work. For commuters, an early-morning weather check shapes whether they leave at 6:30 or 7:30. For students watching the forecast, the uncertainty itself is distracting — and the wrong guess means a missed alarm or a wasted morning.
This guide exists to reduce that uncertainty. It explains how Ontario school boards actually make closure decisions, what weather conditions carry the most weight, how the city you live in changes the calculation, and how to get a useful probability estimate before the official announcement drops.
How Ontario School Boards Actually Decide
Ontario has 72 district school boards — a figure sourced from the Ontario Ministry of Education school board directory — and no two use exactly the same criteria. But the decision process follows a broadly consistent structure across the province.
The Early-Morning Window
Most boards begin their overnight assessment around 3:30–4:00 AM, when transportation supervisors start contacting road crews and reviewing Environment Canada alerts. Here is a rough timeline of what happens before your phone buzzes:
- 3:30–4:30 AM — Transportation supervisors review overnight weather data and contact municipal road authorities
- 4:30–5:15 AM — Bus drivers and school principals may be consulted; preliminary internal calls made
- 5:15–5:45 AM — Senior staff confer on a final recommendation
- 5:45–6:30 AM — Official decision posted on the board's website, app, and social channels
A few large boards — including the Toronto District School Board (TDSB) and Ottawa-Carleton District School Board (OCDSB) — have pushed announcements as early as 5:00 AM when conditions made the outcome clear overnight.
Who Has the Final Call
In most boards, the Director of Education or a designated superintendent has authority to declare a closure. Transportation managers have authority over bus cancellations specifically. These are often separate decisions made in the same window, which is why you can have buses cancelled but schools open.
The Ontario Ministry of Education sets the provincial policy framework for publicly funded education but does not issue individual closure orders. Boards decide independently within that framework.
Ontario School Board Directory: Where to Check
The most common reason families miss a closure announcement is checking the wrong place — a general news site or a neighbour's post rather than their own board's official channel. The boards listed below are the primary ones for the GTA and surrounding regions. Each links directly to the board's weather closure or transportation page where it exists, or the board homepage otherwise.
| Board | Type | Primary Region | Official Closure / Transportation Page |
|---|---|---|---|
| Toronto District School Board (TDSB) | Public | Toronto (City) | tdsb.on.ca — Weather-Related Closures |
| Toronto Catholic District School Board (TCDSB) | Catholic | Toronto (City) | tcdsb.org — School Closures |
| Peel District School Board (PDSB) | Public | Brampton, Mississauga, Caledon | peelschools.org — Closures and Delays |
| Dufferin-Peel Catholic District School Board (DPCDSB) | Catholic | Brampton, Mississauga, Caledon | dpcdsb.org |
| York Region District School Board (YRDSB) | Public | Markham, Vaughan, Richmond Hill, Newmarket | yrdsb.ca — Bus Cancellations |
| York Catholic District School Board (YCDSB) | Catholic | Markham, Vaughan, Richmond Hill, Newmarket | ycdsb.ca |
| Durham District School Board (DDSB) | Public | Oshawa, Whitby, Ajax, Pickering, Clarington | ddsb.ca — School Closures |
| Durham Catholic District School Board (DCDSB) | Catholic | Oshawa, Whitby, Ajax, Pickering, Clarington | dcdsb.ca |
| Halton District School Board (HDSB) | Public | Burlington, Oakville, Milton, Halton Hills | hdsb.ca — School Closures |
| Halton Catholic District School Board (HCDSB) | Catholic | Burlington, Oakville, Milton, Halton Hills | hcdsb.org |
| Ottawa-Carleton District School Board (OCDSB) | Public | Ottawa and surrounding area | ocdsb.ca — Closures and Bus Cancellations |
| Ottawa Catholic School Board (OCSB) | Catholic | Ottawa and surrounding area | ocsb.ca |
Bus Cancellation vs. Full School Closure: A Critical Distinction
Ontario families often treat these as the same thing. They are not, and conflating them leads to real confusion on storm days.
| Situation | School Open? | Buses Running? | What It Means for Families |
|---|---|---|---|
| Bus cancellation only | Yes | No | Families who arrange their own transport may send their child; attendance is not penalised |
| Full school closure | No | No | Building is closed; staff may work remotely; some boards trigger virtual learning days |
| Delayed start | Yes (later) | Sometimes | School begins 1–2 hours late; buses may run on adjusted schedule |
| Early dismissal | Partial | Adjusted | School closes mid-day due to deteriorating conditions |
Bus cancellations happen more frequently than full closures. When roads are passable for cars but not safe for a large vehicle carrying children on rural routes, boards cancel transportation without shutting buildings. Parents receive a "no busing" notice and make their own call about attendance.
Full closures are reserved for conditions severe enough that attending in any form is unsafe or impractical — typically a combination of heavy snowfall, poor visibility, and road conditions that are deteriorating rather than improving.
If you want to understand the spectrum of closure decisions across different regions and school types, the main snow cancellation threshold guide covers the full picture, including elementary versus secondary differences.
How Delayed Starts Work in Ontario
A delayed start (sometimes called a late start or two-hour delay) means the school building itself opens 1–2 hours later than normal — not just buses. Boards use this option when conditions are hazardous at the normal 8:30–9:00 AM opening but are expected to improve significantly by mid-morning.
Not all Ontario boards use delayed starts as a routine tool. Some prefer to avoid the operational complexity and go straight from "schools open" to "full closure" with no intermediate step. Check your specific board's winter weather communication at the start of each school year to know whether a delayed start is in their toolkit. The TDSB weather closure page describes the options they use, as does the OCDSB closures page.
Public vs. Catholic Boards: Do Policies Differ?
Ontario operates parallel public and Catholic district school boards in most of the province, and a question that comes up regularly is whether they coordinate closure decisions. The short answer is: sometimes, but not always — and the divergence happens most often on borderline storm days rather than major events.
Public and Catholic boards in the same city share the same roads and the same weather, and they often — though not always — reach the same conclusion. In Ottawa on a significant storm day, you might see the OCDSB and OCSB announce bus cancellations within minutes of each other because their transportation assessment timelines overlap. In smaller communities, the boards may share a transportation consortium that makes a single joint decision on busing, even if building-closure authority remains separate.
The GTA Pairing Problem
In the Greater Toronto Area, every public board has a parallel Catholic board operating across roughly the same geography. The pairings that most commonly cause confusion:
- Toronto: TDSB (public) and TCDSB (Catholic) — fully independent operations, separate transportation contracts. On borderline days, one has occasionally cancelled buses while the other has not.
- Peel: PDSB (public) and DPCDSB (Catholic) — serve the same Brampton/Mississauga geography. Closure decisions are made independently.
- York Region: YRDSB (public) and YCDSB (Catholic) — some shared consortium busing arrangements exist in parts of the region, which can produce more aligned transportation decisions than purely independent boards.
- Durham: DDSB (public) and DCDSB (Catholic) — shared busing arrangements exist through the Durham Student Transportation Services consortium, making transportation decisions more likely to be aligned.
- Halton: HDSB (public) and HCDSB (Catholic) — Halton Student Transportation Services handles busing for both boards jointly, so transportation cancellations are typically announced together.
Where divergence happens most visibly:
- Large cities with independent operations: Toronto's TDSB and TCDSB each maintain their own transportation contracts and decision chains. On borderline storm days, one board has occasionally kept schools open while the other cancelled buses.
- Different student population geography: If one board draws more students from rural routes and the other from urban neighbourhoods, their transportation risk profiles differ even in the same municipality.
- Administrative conservatism: Individual superintendents set the culture. Some err toward caution; others toward continuity.
The practical takeaway for families: check your specific board, not just your city. If you have children in both a public and a Catholic school, those boards may reach different decisions on the same morning.
| Board Pair | Transportation Arrangement | Typical Coordination |
|---|---|---|
| OCDSB & OCSB (Ottawa) | Partial shared busing consortia in some areas | Usually aligned on bus cancellations; building closures decided separately |
| TDSB & TCDSB (Toronto) | Fully independent | Often aligned but occasional divergence on borderline days |
| HDSB & HCDSB (Halton) | Joint — Halton Student Transportation Services | Transportation cancellations typically announced together; building closures still decided independently |
| DDSB & DCDSB (Durham) | Joint — Durham Student Transportation Services | Bus cancellations typically aligned; building decisions remain independent |
Snowfall Thresholds: A Realistic Picture
Ontario boards do not publish a fixed snowfall threshold that automatically triggers closure — and there is good reason for that. A 12 cm snowfall that lands evenly between 10 PM and 4 AM, with roads cleared by 6 AM, is very different from 12 cm falling from 4 AM to 8 AM. The former may see schools open; the latter almost certainly means buses cancelled.
With that context, here is a general guide to how snowfall totals tend to influence decisions in southern Ontario, based on observed patterns over several winters:
| Snowfall Total | Timing | Typical Outcome |
|---|---|---|
| 2–5 cm | Any | Schools open; some rural bus delays possible |
| 6–10 cm | Overnight (cleared by 6 AM) | Schools open; urban boards likely unaffected |
| 6–10 cm | Morning rush (4–8 AM) | Bus cancellations likely in rural areas; urban boards often open |
| 10–20 cm | Overnight | Bus cancellations common; full closure if accumulation continues into morning |
| 10–20 cm | Morning rush | Full closures likely across most boards |
| 20+ cm or blizzard | Any | Full closure across virtually all boards; freezing rain compounds this |
These patterns reflect general trends, not guarantees. Boards also consider whether the previous day saw incomplete road clearing, whether a second storm system follows, and how much warning staff had to prepare.
Freezing rain deserves a separate note: even 2–3 mm of ice accretion can trigger bus cancellations where 8 cm of snow would not, because ice-coated roads are far more dangerous for large vehicles. Environment Canada's public alerting criteria describe the thresholds at which freezing rain advisories and warnings are issued — these alerts are treated seriously by Ontario transportation managers. In the Lake Erie and Lake Ontario snowbelt regions — including areas south and east of Lake Simcoe — lake-effect events can deposit 20–30 cm in just a few hours, overwhelming road crews and making thresholds less meaningful.
Urban vs. Rural: Why the Answer Differs by Region
Ontario covers 1.07 million km² and contains everything from downtown Toronto to remote northern communities. Weather tolerance varies significantly across this geography.
| Region | Typical Tolerance | Key Factors |
|---|---|---|
| Toronto (TDSB / TCDSB) | High — rarely closes | Dense road network, 24/7 plowing, many walking students, transit options |
| Ottawa (OCDSB / OCSB) | Moderate — closes on significant events | Experienced with heavy snowfall; long bus routes in Kanata/Orleans suburbs increase sensitivity |
| Hamilton / Niagara | Moderate — lake-effect sensitive | Escarpment weather patterns; heavy lake-effect events off Lake Erie can be very localised |
| London / Windsor | Moderate | Exposed to Lake Erie lake-effect; freezing rain risk higher due to proximity to US border weather systems |
| Rural / Northern Ontario | Low — closes earlier | Long bus routes on secondary roads, fewer plowing resources, extreme cold events, Indigenous community schools with unique policies |
| Snowbelt (Barrie / Collingwood) | High local tolerance, but large events still close | Residents accustomed to heavy snow; Georgian Bay lake-effect can be exceptional |
The Toronto dynamic is worth understanding specifically. The TDSB — Canada's largest school board — serves students across an urban and suburban area where the majority either walk, take TTC, or are driven. Bus route coverage is therefore less central to its closure decision than it is for a board like Upper Grand District School Board, where elementary students travel long distances on rural concession roads.
Ottawa presents a middle case. The city receives significant snowfall and road crews are well-resourced. But the outer suburban routes into Kanata, Orleans, and communities toward the Quebec border cover distances that make bus cancellations common even when central Ottawa roads are clear. Environment Canada's Ottawa climate normals (1991–2020) show mean annual snowfall above 220 cm at the airport station — context for why the city is generally well-prepared for winter but still sees meaningful closures on serious events.
To illustrate the range of sensitivity across Ontario boards, here is a rough closure-frequency framing based on observed patterns across recent winters. These are observational categories, not official board-published statistics:
| Frequency Category | Typical Full Closures per Season | Representative Boards | Primary Driver |
|---|---|---|---|
| Rarely closes | 0–1 full closures | TDSB, TCDSB (Toronto) | Dense urban network; most students do not rely on buses |
| Closes on significant events | 2–4 full closures | OCDSB / OCSB (Ottawa), HWDSB (Hamilton), TVDSB (London) | Mix of urban and suburban routes; freezing rain events are the main trigger |
| Closes regularly | 4–8 full closures | Bluewater DSB, Upper Grand DSB, Near North DSB | Heavy reliance on rural and secondary road bus routes |
| Closes frequently | 8+ full closures or bus-cancel days | Rainbow DSB (Sudbury), Near North DSB northern routes, northern First Nation school authorities | Extreme cold events, extended lake-effect, and long rural routes on unclassified roads |
The Factors That Matter More Than Snowfall Totals
Transportation managers do not look at one number and make a call. They weigh several conditions at once — and snowfall total, the most visible of them, is often not the one that tips the decision.
| Factor | Why It Matters | High-Impact Threshold (general) |
|---|---|---|
| Storm timing | Snow falling during the decision window (4–7 AM) is most disruptive; overnight snow can be cleared before buses run | Active snowfall at 5:00 AM significantly raises closure probability |
| Wind / blowing snow | Reduces visibility on highways and secondary roads; can make conditions dangerous even after plowing | Wind gusts above 60 km/h combined with snow increase risk sharply |
| Freezing rain / ice | Far more hazardous per cm than snow; dramatically increases vehicle slide risk | Any freezing rain advisory from Environment Canada is treated seriously — see ECCC alert criteria |
| Temperature and wind chill | Extreme cold can trigger closure independently of precipitation | Wind chill warnings at −35°C or colder prompt closures in northern/rural boards |
| Road surface condition | Transportation managers assess secondary road conditions directly; a plowed arterial road does not guarantee secondary roads are safe | Unplowed secondary roads at bus departure time is often decisive |
| Storm progression | A storm that has passed and is clearing improves rapidly; a storm still intensifying at 5 AM is treated conservatively | Intensifying conditions at decision time lean toward closure |
Ontario Winter Case Examples
Abstract thresholds make more sense next to real situations. Where possible, the examples below reference publicly documented Ontario weather events; where they describe recurring patterns rather than a single incident, that is noted.
January 2022 — Ontario Blizzard, Multiple Boards Close
A powerful winter storm in late January 2022 brought 30–50 cm to parts of eastern and southern Ontario over roughly 24 hours, with wind gusts above 80 km/h producing near-zero visibility on major highways. Dozens of school boards across eastern Ontario, including the OCDSB, OCSB, and boards in the Kingston and Trenton corridors, cancelled school for multiple consecutive days. Toronto-area boards mostly remained open during the initial storm but cancelled buses as conditions peaked. The event illustrated how storm duration — not just accumulation — forces consecutive-day decisions that a single-night snowfall does not.
December 2013 — The Great Ontario Ice Storm
The ice storm of December 21–22, 2013 is one of the most referenced Ontario winter events in recent memory. Freezing rain deposited 25–40 mm of ice across the Greater Toronto Area and surrounding regions, knocking out power to more than 300,000 homes. Toronto Hydro's 2013 Ice Storm Report documented the scale of the outage publicly. Schools were closed not just for safety during the storm but for days afterward as power outages affected buildings and road conditions remained hazardous. The event remains a benchmark example of why freezing rain — even without significant snowfall — can produce longer and more disruptive closures than a heavy snowstorm.
Composite: Georgian Bay Lake-Effect Snowband (Recurring)
This pattern repeats several times each winter in Grey and Bruce Counties. Lake-effect snow off Georgian Bay builds a persistent snowband that can drop 15–25 cm in just a few hours across a corridor only 30–50 km wide. Bluewater District School Board and Trillium Lakelands District School Board are most frequently affected. What makes these events uniquely difficult to predict is that the snowband can shift north or south by 20 km overnight — meaning actual accumulation at bus-route level often differs sharply from what regional models showed at midnight. A board's transportation supervisor driving secondary roads at 4:30 AM may find 8 cm where the forecast said 3.
Composite: Overnight Dump with Clear Morning (Common Southern Ontario Pattern)
A low-pressure system passes through between 9 PM and 3 AM, depositing 12–15 cm. By 4 AM, road crews are active on primary routes. Wind is light. Temperature is around −8°C. This is the scenario where urban and rural boards most visibly diverge: TDSB and London-area boards typically stay open because their primary road networks are largely cleared by bus time. Upper Grand DSB, Renfrew County DSB, and boards with long concession-road routes often cancel buses because secondary roads are still covered when drivers would need to depart at 6:00–6:30 AM.
Composite: The 401-Corridor Freezing Rain Event (Southwestern Ontario)
Freezing rain events tracking along the 401 corridor between Windsor and Kingston are among the most disruptive per-millimetre events in Ontario. An overnight deposit of 4–6 mm of ice glazes residential streets and rural concessions simultaneously. Sand trucks improve arterial roads but cannot restore traction on side streets. This type of event consistently produces multi-board closures across Thames Valley DSB, Thames Valley Catholic DSB, and eastward to Limestone DSB. What distinguishes these events from snowstorms is their near-simultaneous impact: there is no geographic gradient that lets rural boards close while urban boards stay open.
For a broader perspective on how closure decisions differ by province and territory, the Canada snow day calculator guide covers the national picture, including how Ontario compares with Quebec, Alberta, and BC approaches.
Decision Matrix: Reading the Signs Before 6 AM
The table below is the closest thing to a practical field guide for assessing closure probability while you wait for an official announcement. It combines the factors discussed above into a quick-read format. Each row reflects a condition; the more conditions that apply simultaneously, the higher the probability of some form of cancellation.
| What You're Seeing at 5 AM | Effect on Probability | Applies Most To |
|---|---|---|
| Snow still actively falling and accumulating | Significant increase — crews cannot clear ahead of buses | All boards, especially rural |
| Snow stopped, roads partially cleared | Moderate — outcome depends on secondary road status | Rural and suburban boards most sensitive |
| Environment Canada snowfall warning still active | Increase — boards treat active warnings as a signal | All boards |
| Freezing rain advisory or warning active | High increase — often triggers bus cancellations even with small accumulation | All boards |
| Wind gusts above 60 km/h | Increase — blowing snow re-covers cleared roads; visibility risk for bus routes | Rural highways and open areas |
| Wind chill at or below −35°C | May trigger closure independently of precipitation | Northern Ontario boards primarily |
| Storm system clearing and temperatures rising | Decrease — improving conditions favour staying open | Reduces pressure on all boards |
| Previous day's roads incompletely cleared | Increase — compounding effect on secondary roads | Rural boards, multi-day events |
| Neighbouring boards already announced closure | Moderate signal — boards monitor peers but decide independently | Shared-geography boards |
This matrix is an observational guide, not a scoring system. No single factor is automatically decisive. The value is in recognising combinations: a storm still falling at 5 AM + a freezing rain advisory + rural secondary routes = high confidence in bus cancellations at minimum.
What to Do Before the Official Decision
The window between when you wake up and when your board posts its decision — typically 5:00 to 6:30 AM — is when preparation matters most. Here is a practical checklist for families and commuters:
- Sign up for your board's direct alerts. Most Ontario boards offer email or SMS notifications. These arrive before social media posts and before local news outlets update. Find yours by searching "[your board name] + school closure alerts," or use the direct links in the board directory table above.
- Check Environment Canada first. If an active warning is in place, the probability of some form of cancellation is already elevated. A "no warning" status at 4:30 AM meaningfully reduces it. Visit weather.gc.ca or the WeatherCAN app.
- Have a backup childcare plan ready before storm season, not the morning of. Identifying a neighbour, relative, or daycare that can take a child on short notice is far easier done in November than at 6:10 AM on a January storm morning.
- Check your board's transportation page, not just the school homepage. Bus cancellations and school closures are often posted on different pages of board websites. The transportation or student services section is usually where cancellations appear first.
- Use a snow day calculator the night before. A probability estimate the evening before a forecast storm helps you decide whether to arrange backup care proactively rather than reactively. The snow day tomorrow guide explains how to read evening forecasts for the next morning.
- For commuters: assume worse-than-forecast conditions on secondary roads. Even when highways are cleared, rural concession roads and residential streets may remain hazardous for hours after the official storm period ends.
How Snow Day Calculators Work — and Where They Fall Short
A snow day calculator combines weather forecast data with historical board behaviour to produce a probability estimate. It is genuinely useful, but the limits are worth understanding clearly before you rely on one at 5 AM.
What Goes Into a Prediction
Better calculators draw on several data streams simultaneously:
- Forecast snowfall totals and confidence intervals from weather services
- Storm timing relative to the 4–7 AM decision window
- Temperature, wind speed, and precipitation type (snow vs. rain vs. ice)
- Historical patterns for the specific board or region
- Whether a warning or advisory is in effect from Environment Canada
Our data sources page explains which weather APIs and forecast inputs are used for the predictions on this site. The weather APIs page covers the technical layer.
Where Predictions Are Reliable
Probability estimates are most useful when storm conditions are clearly severe or clearly mild. When a forecast calls for 25 cm overnight with sustained winds, the prediction will reflect high closure probability — and that will usually be right. When a forecast shows 3 cm with no ice, a low probability estimate is equally reliable.
The harder cases are the 8–12 cm range, where board tolerance, storm timing, and local road conditions all interact in ways no external tool can fully capture.
Where Predictions Have Limits
- Calculators cannot know whether your board's road crews finished clearing at 5:30 AM or 7:00 AM
- Local lake-effect events can be hyper-localised — a snowband 20 km wide may be missed by regional forecast models
- Freezing rain amounts are harder to forecast than snowfall, and a small ice accretion can change outcomes sharply
- Individual board leadership varies — some directors are more conservative than others in ambiguous conditions
- Elementary vs. secondary school closures can differ within the same board — see the school and college closure calculator guide for detail on how age-level policies vary
The most accurate snow day calculator guide covers how different tools approach these uncertainties and what to look for when comparing prediction services. For a specific comparison with a major weather provider, see the AccuWeather snow day calculator comparison.
A probability-based calculator gives you a percentage rather than a yes/no, which is more honest about the genuine uncertainty involved.
Sources Used in This Guide
The following sources informed the observations, thresholds, and examples in this article. Where a claim is drawn from a specific source, that source is noted. General pattern descriptions reflect multi-season observation rather than a single document.
- Environment Canada — Public Alerting Criteria and Definitions: Wind-chill warning thresholds and freezing rain advisory criteria. canada.ca — Alert criteria and definitions
- Toronto District School Board — Weather-Related School Closures: Publicly posted board policy on closure authority and communication procedures. tdsb.on.ca — Weather-Related School Closures
- Toronto Catholic District School Board — School Closures: Board communications on closure procedures. tcdsb.org — School Closures
- Ottawa-Carleton District School Board — School Closures and Bus Cancellations: Board communications on the announcement timeline and transportation decision process. ocdsb.ca — School Closures and Bus Cancellations
- Peel District School Board — School Closures and Delays: peelschools.org — Closures and Delays
- York Region District School Board — Bus Cancellations: yrdsb.ca — Bus Cancellations
- Durham District School Board — School Closures: ddsb.ca — School Closures
- Halton District School Board — School Closures: hdsb.ca — School Closures
- Toronto Hydro — 2013 Ice Storm Response: Publicly reported figure of 300,000+ customer outages referenced in post-storm communications. torontohydro.com — 2013 Ice Storm Report
- Ontario Ministry of Education — School Board Directory: Source for the 72 district school board count in Ontario and complete board listing. ontario.ca — School Board Directory
- Ontario Ministry of Education — Ministry Overview: Provincial education framework and board governance. ontario.ca — Ministry of Education
- Environment Canada — Ottawa Climate Normals 1991–2020: Seasonal snowfall average for Ottawa (Intl Airport station) used to characterise typical annual accumulation. climate.weather.gc.ca — Ottawa Climate Normals
- Environment Canada — Historical Storm Data Archive: January 2022 Ontario blizzard event documentation. weather.gc.ca — Warning Archive
- Our own data sources and methodology: Data sources page · Weather APIs page · Full references list
Editorial Methodology & Correction Policy
This guide draws on publicly available school board closure announcements and transportation policies, Environment Canada historical weather data and alert archives, and the author's multi-year observation of Ontario board behaviour across winter seasons. Specific sourced claims are linked in the Sources section above.
Snowfall ranges and closure likelihood descriptions reflect general observed patterns in southern Ontario, not statistical analysis of a formal dataset. Timing windows cited (such as "5:45–6:30 AM" for announcements) represent typical ranges observed across major boards and may not apply to every board or every storm. They are intended as orientation, not guarantees. Northern Ontario and snowbelt regions behave differently, and this guide notes those differences where relevant.
The figure of 72 district school boards is sourced from the Ontario Ministry of Education school board directory, which is subject to occasional restructuring. Ottawa's seasonal snowfall figure (220+ cm) is derived from Environment Canada climate normals for Ottawa; actual seasonal totals vary. The closure-frequency table in the regional section represents observational categories based on multi-season pattern review — it is not a statistically derived dataset and should be read as orientation, not measurement. Board links in the directory table were verified as of July 2026; board websites periodically restructure their pages and links may change.
We do not make precision accuracy claims for our snow day calculator. Statements about prediction quality refer to the general capability of weather-informed models, not a controlled evaluation of this site's specific tool.
Correction Policy
If you identify a factual error, an outdated policy reference, an incorrect or broken board link, or a board-specific detail that is wrong, please contact us. We review correction requests and update the article when errors are confirmed. Substantive corrections are noted in the modification date at the top of the article. Minor clarifications are made without a separate note. Board policies change, particularly after provincial restructuring or leadership transitions — if you know your board's policy has recently changed, we welcome that information.
Frequently Asked Questions
How much snow causes school closures in Ontario?
There is no fixed number. Boards weigh snowfall alongside timing, road conditions, and precipitation type. As a rough guide, 10–15 cm falling overnight and largely cleared by 6 AM is less disruptive than 8 cm still falling actively at 5:30 AM. Freezing rain changes the calculation entirely — even small ice amounts can trigger widespread bus cancellations.
What is the difference between bus cancellation and full school closure?
A bus cancellation means the board has suspended transportation but left the building open. Families who can arrange their own drop-off may still attend; most boards do not penalise absences on bus-cancellation days. A full school closure means the building itself is closed and students are expected to stay home.
Do Ontario schools close for cold weather alone, without snow?
Yes, in some circumstances. Boards in northern Ontario and rural areas may close when Environment Canada issues an extreme cold warning, typically at wind chills approaching −35°C or colder. The risk of students waiting for buses in those conditions, combined with potential vehicle reliability issues, can be enough to prompt closure without precipitation.
When are Ontario snow day decisions announced?
Most boards post decisions between 5:30 AM and 6:30 AM. Some post preliminary transportation alerts as early as 5:00 AM. The safest approach is to check your board's website or app directly — social media posts can lag behind official channels. See the board directory table above for direct links to each board's official closure page.
Why does Toronto stay open when smaller towns close?
Toronto's road network is denser, more frequently plowed, and serves more students who walk or use transit rather than school buses. When buses are cancelled, the impact on attendance is smaller. Rural boards depend on buses covering long routes on secondary roads that may not be cleared for hours after main roads are passable.
How does a snow day calculator predict closures?
A calculator combines forecast snowfall, storm timing, temperature, wind, and historical board behaviour to generate a probability. It is an informed estimate — useful for planning — but not a substitute for the official announcement from your board. Always confirm through your board's official channels before making childcare or schedule decisions.
What is a delayed start, and which Ontario boards use it?
A delayed start means school opens 1–2 hours later than normal. Boards use this when morning conditions are hazardous but expected to improve. Buses may run on an adjusted schedule or not at all for the first run. Not all Ontario boards use delayed starts — some go straight from "schools open" to "full closure." Check your specific board's winter weather communication at the start of each year. The TDSB and OCDSB both describe the options they use on their official closure pages.
Do Ontario boards use virtual learning days for snow days?
Practice varies considerably. Some boards incorporated remote learning into their emergency plans after the pandemic period; others treat severe weather days as cancelled instructional time with no remote component. A closure does not automatically mean virtual learning — check your specific board's back-to-school communication at the start of each year for their current policy.
If buses are cancelled but school is open, does attendance count against my child?
In most Ontario boards, bus cancellation days are treated as excused absences if a family cannot arrange alternative transportation. Most boards explicitly state this in their transportation policies: students are not penalised academically for missing school when buses are cancelled. Schools remain open and instruction continues for those who do attend. Confirm your specific board's policy, as wording varies — the board links in the directory table above lead to transportation pages where this information is typically published.
Can public and Catholic boards in my city reach different closure decisions?
Yes. Public and Catholic boards operate independently and make their own closure decisions even when they share the same city and weather. On borderline storm days, it is possible — though not common — for one board to cancel buses while the neighbouring board does not. Always check your specific board's announcement rather than assuming a neighbour's board decision applies to yours. The public vs. Catholic section above covers which GTA board pairs share transportation arrangements and which operate fully independently.
Where can I find official Ontario school closure notices?
Each board maintains its own website and, in most cases, an email or text alert system. There is no central provincial registry for closure announcements. The board directory table above provides direct links to the official closure or transportation pages for the largest Ontario boards. For boards not listed there, the Ontario Ministry of Education school board directory lists every funded board with links to their official sites.