Ontario · Multi-model forecast · 2026–27 season
Snow Day Predictor OntarioWill school be cancelled tomorrow in Ontario?
Live overnight forecast for every Ontario postal code — from the TDSB and Peel coverage area through Ottawa, Hamilton, London, Kitchener-Waterloo, Sudbury, and Thunder Bay. The predictor tunes to GTA bus-cancellation patterns or Northern Ontario closure thresholds automatically based on your location.
Multi-model forecast, five-factor closure engine, province-aware results. No sign-up, no tracking of your queries.
What makes Ontario unique
Ontario has the most varied snow day behaviour in Canada — the GTA cancels buses for weather that would shut down every district on coastal British Columbia, while Northern Ontario boards operate through conditions that would close schools province-wide further south. No other province needs two distinct regional profiles to forecast accurately.
Province overview
Ontario snow day forecast — what makes the province different
Ontario stretches roughly 1,700 km north to south and spans climate zones from the Lake Erie shoreline to the James Bay coast. No single closure threshold fits the whole province, which is why our forecast uses two distinct regional profiles for Ontario rather than one. The Greater Toronto Area, Hamilton, and southwestern Ontario boards (Peel, York, Halton, Durham, TDSB, Hamilton-Wentworth, Thames Valley) operate through 10–12 cm of overnight snow regularly, cancelling buses well before they close school buildings. Rural and Northern Ontario boards (Rainbow DSB in Sudbury, Lakehead DSB in Thunder Bay, Algoma in Sault Ste. Marie, Keewatin-Patricia further north) face longer bus routes, lake-effect bands off Lakes Huron and Superior, and wind-chill values that drive cold-day closures the south rarely sees.
Most Ontario closure decisions are coordinated through student transportation consortia (STSCO, STSWR, HSTS, STOPR, Toronto Student Transportation Group, OSTA) rather than individual school boards. That structure produces Ontario’s distinctive bus-cancelled-but-school-open day — common in the GTA and a key reason our predictor returns school closure and bus cancellation as two separate probabilities. The Toronto District School Board, the largest in the province, has not fully closed for snow in many recent winters; its buses, by contrast, are cancelled several times each season.
Lake-effect snow is Ontario’s signature weather hazard. Bands forming over Lake Huron, Georgian Bay, Lake Ontario, and Lake Erie can deposit 20–40 cm in a narrow corridor while the next county over sees nothing. Our forecast pulls hourly data at your exact coordinates rather than averaging across a broad area, so a lake-effect band sitting over Barrie or Owen Sound shows up correctly in the prediction even when the rest of the GTA is quiet.
15 cities covered
Snow day predictor by Ontario city
Every Ontario city below has its own dedicated forecast page that runs the predictor automatically for that location.
Largest district in Canada; rarely closes buildings, cancels buses several times each winter.
Peel and Dufferin-Peel Catholic typically align; STOPR cancels buses for the whole region.
Same coverage as Mississauga; STOPR transportation calls usually apply to both.
Lake-effect snow off Lake Ontario; Niagara Escarpment can intensify bands.
Ottawa Valley snow squalls; coordinated bus cancellations through OSTA.
Lake Huron snow belt; among the heaviest seasonal snowfall in Ontario.
STSWR coordinates buses across Kitchener, Waterloo, and Cambridge.
Same STSWR coverage as Kitchener; closures align across the region.
Heavy Georgian Bay lake-effect bands; high closure frequency relative to GTA.
Lake Ontario shoreline; Tri-Board handles transportation across the region.
Southernmost Canadian schools; freezing rain more common than heavy snow.
Significant lake-effect snow off Georgian Bay; cold-driven closures common.
Lake Superior snow events; among the coldest Ontario districts.
York Region snow squall corridor north of the GTA.
Same YRDSB coverage as Markham, Aurora, Richmond Hill, Newmarket.
School boards
Ontario school boards and their closure patterns
A snapshot of the boards we model when generating Ontario forecasts, grouped by region.
Greater Toronto Area
- Toronto District School Board (TDSB)
Canada’s largest school board. Rarely closes buildings outright; bus cancellations through Toronto Student Transportation Group are common.
- Toronto Catholic District School Board (TCDSB)
Closure decisions usually align with TDSB on weather days.
- Peel District School Board
Mississauga, Brampton, and Caledon. Bus decisions through STOPR.
- Dufferin-Peel Catholic DSB (DPCDSB)
Catholic counterpart to Peel; same STOPR transportation.
- York Region District School Board (YRDSB)
Markham, Vaughan, Newmarket, Aurora, Richmond Hill. Heavy snow squall exposure.
- York Catholic DSB (YCDSB)
Catholic counterpart to YRDSB.
- Halton DSB and Halton Catholic DSB
Oakville, Burlington, Milton, Halton Hills. Halton STS coordinates buses.
- Durham DSB and Durham Catholic DSB
Oshawa, Whitby, Pickering, Ajax. Frequent Lake Ontario lake-effect.
Ottawa & Eastern Ontario
- Ottawa-Carleton DSB (OCDSB)
Largest board in Eastern Ontario; serves Ottawa and surrounding rural areas.
- Ottawa Catholic School Board (OCSB)
Catholic schools across Ottawa.
- Upper Canada DSB
Kingston east through Cornwall and the Ottawa Valley.
- CECCE and CEPEO
French-language Catholic and public boards across Eastern Ontario.
Southwestern Ontario
- Thames Valley DSB (TVDSB)
London, Woodstock, St. Thomas. Lake Huron snow belt exposure.
- London District Catholic SB (LDCSB)
Catholic counterpart to TVDSB.
- Hamilton-Wentworth DSB (HWDSB)
Hamilton and surrounding municipalities. Lake Ontario lake-effect.
- Hamilton-Wentworth Catholic DSB (HWCDSB)
Catholic counterpart to HWDSB.
- Waterloo Region DSB
Kitchener-Waterloo-Cambridge. Transportation through STSWR.
- Greater Essex County DSB (GECDSB)
Windsor and Essex County; southernmost schools in Canada.
- Lambton-Kent DSB
Sarnia and Chatham areas. Heavy Lake Huron snow events.
Northern Ontario
- Rainbow DSB
Sudbury and surrounding districts. Significant Georgian Bay lake-effect and cold.
- Algoma DSB
Sault Ste. Marie. Lake Superior storm exposure.
- Lakehead DSB
Thunder Bay. Coldest Ontario district by wind-chill metrics.
- Keewatin-Patricia DSB
Northwestern Ontario remote communities. Extreme cold–driven closures.
- Near North DSB
North Bay and Parry Sound regions.
Bus cancellations
How Ontario student transportation cancels buses
In Canada, bus cancellations are a separate decision from full school closures — and most regions coordinate this through a student transportation consortium rather than each individual board.
- Toronto STGToronto Student Transportation Group
TDSB and TCDSB buses across Toronto.
- STOPRStudent Transportation of Peel Region
Peel DSB and DPCDSB across Mississauga, Brampton, Caledon.
- STSCOStudent Transportation Services of Central Ontario
Multiple boards in Simcoe, Muskoka, and Northumberland.
- STSWRStudent Transportation Services of Waterloo Region
Kitchener, Waterloo, Cambridge.
- HSTSHalton Student Transportation Services
Oakville, Burlington, Milton, Halton Hills.
- OSTAOttawa Student Transportation Authority
Ottawa-Carleton public and Catholic boards.
- Tri-Board STSTri-Board Student Transportation Services
Kingston east through to Brockville and the upper Ottawa Valley.
Regional weather patterns
Ontario snow zones and storm patterns
The signature weather phenomena our forecast accounts for across Ontario.
- Lake Ontario / Toronto north shore
Lake-effect bands set up when northwesterly winds cross open water in early winter. Hamilton, Toronto north, Pickering, and Oshawa see the heaviest accumulation.
- Georgian Bay / Simcoe County
Barrie, Orillia, Owen Sound, Collingwood and Wiarton sit in one of Canada’s most reliable lake-effect snow zones. Single-day totals of 30+ cm are routine.
- Lake Huron snow belt
Sarnia north through Goderich, Kincardine, and Grand Bend regularly sees the heaviest seasonal snowfall in Ontario.
- Niagara Escarpment
Topographic lift over the escarpment intensifies snowfall bands across St. Catharines, Niagara, and southern Hamilton.
- Lake Superior shore
Thunder Bay, Wawa, and Sault Ste. Marie face Lake Superior storm systems that can produce blizzard conditions through late spring.
- James Bay Lowlands
Northeastern Ontario communities (Moose Factory, Moosonee, Attawapiskat) experience extreme cold–driven closures more than snow.
History
Notable Ontario snow days in recent winters
Recent storms and cold events that shaped how Ontario school boards make the morning call.
Southern Ontario blizzard
January 14, 2022A blizzard delivering 30+ cm of snow with 70 km/h winds closed every major GTA board. TDSB, Peel, YRDSB, Halton, and Durham all closed buildings on the same day — an unusual event in the GTA where bus cancellations more typically substitute for full closures.
Greater Toronto ice storm
December 21, 2013Freezing rain accumulated up to 30 mm across the GTA, knocking out power for over 300,000 homes and closing schools for multiple days into the holidays. The textbook case of why our forecast weights freezing rain heavily — 2 mm of ice closes more Ontario schools than 10 cm of dry snow.
Ottawa Snow Day
February 27, 2008Ottawa-Carleton boards closed after a multi-day storm dropped over 40 cm on the capital region. OC Transpo also suspended service — a rare full-network shutdown.
Eastern Ontario ice storm
April 14, 2018A late-season ice storm coated trees and roads across Eastern Ontario, Kingston, and the Ottawa Valley. Boards closed for two days. A reminder that Ontario snow day risk does not end in March.
Polar vortex closures
February 2019Wind chill values below −45 °C closed schools across Lakehead DSB, Rainbow DSB, and Keewatin-Patricia for safety reasons. Snowfall was incidental; cold was the trigger.
Toronto Snowstorm
January 1999Multiple back-to-back storms over two weeks deposited 118 cm of snow on Toronto. Mayor Mel Lastman called in the Canadian Armed Forces for snow removal. Schools closed for days. The benchmark Ontario winter event of the modern era.
FAQ
Ontario snow day frequently asked questions
The 9 questions Ontario parents and teachers ask us most often.
Will TDSB close tomorrow?
Type your Toronto postal code or "Toronto, Ontario" into the predictor at the top of this page to see tomorrow’s school closure probability for the Toronto District School Board. TDSB closures of school buildings are rare in any given storm; bus cancellations through Toronto Student Transportation Group are far more common. Both probabilities are returned.
Are Toronto school buses cancelled today?
For the official decision, check the Toronto Student Transportation Group bus delay app or TDSB’s alerts. Our predictor returns an advance probability the night before based on the overnight forecast, but the official call is made between 5:30 and 6:30 am the day-of.
Why does the GTA cancel buses more often than schools?
Ontario’s system separates building operations from bus operations. Many GTA schools are within walking distance of dense residential neighbourhoods, so the board can keep buildings open while cancelling the long-distance bus routes that serve outlying areas. The result is that bus cancellations happen on weather days that would not justify a full closure.
What snowfall amount typically closes Ontario schools?
GTA boards commonly cancel buses around 10–15 cm of overnight accumulation, with full closures reserved for 20+ cm events combined with wind or ice. Rural and Northern Ontario boards tend to close at lower accumulations because of longer bus routes and limited plowing. Our forecast applies these regional differences automatically.
Does the predictor cover Northern Ontario?
Yes — Sudbury, Thunder Bay, North Bay, Sault Ste. Marie, Kenora, Timmins, and remote James Bay communities are all supported. Northern Ontario coordinates use our rural Ontario profile, which applies different snow and wind-chill thresholds than the GTA profile.
What is Ontario’s snowfall warning threshold?
Environment and Climate Change Canada issues a Snowfall Warning for Ontario when 15 cm or more of snow is expected within 12 hours. The threshold drops to 10 cm/12 hours in lake-effect zones where heavy bursts are common. Snowfall warnings carry weight in our forecast but do not by themselves guarantee a closure.
When does Ontario get lake-effect snow?
Lake-effect snow forms when cold air crosses still-warm lake water. The season typically runs from November through January, with the heaviest bands occurring before the lakes freeze over. Toronto north, Barrie, Owen Sound, Hamilton, London, and Sudbury are the most reliable lake-effect zones in the province.
Will school be cancelled tomorrow in Ottawa?
Enter your Ottawa postal code or "Ottawa, Ontario" above. Ottawa closures are coordinated between OCDSB, OCSB, and OSTA (Ottawa Student Transportation Authority). Ottawa Valley snow squalls and freezing-rain events along the Rideau corridor are the most common closure triggers.
How is the GTA forecast different from the Northern Ontario forecast?
Our predictor uses two distinct regional profiles. The GTA profile applies a 15 cm snow threshold and a −35 °C wind-chill threshold, reflecting the higher snow tolerance of TDSB-area boards and their dense plowing infrastructure. The rural and Northern Ontario profile uses lower snow thresholds (12 cm) and colder wind-chill thresholds (−38 °C), reflecting longer rural bus routes and the operational expectations of Lakehead, Rainbow, Algoma, and other northern boards.
Other provinces
Snow day forecasts for the rest of Canada
Each province has its own dedicated forecast hub with local school boards, weather patterns, and FAQs.
Freezing-rain corridor along the St. Lawrence; CSS service centres coordinate by region.
Coastal districts close at 8 cm; interior boards mirror Prairie tolerance.
Highest snow tolerance in Canada; chinook recovery days are routine.
Wind-chill driven closures; outdoor recess cancels before classes do.
Blizzards and wind chill drive closures; snowfall alone rarely enough.
Atlantic nor’easters; HRCE announces via its app the night before for major storms.
Bay of Fundy storms and freezing-rain events.
NLESD is among the most weather-tolerant districts in Canada.
Coastal wind events and rural road exposure; single province-wide board.
Extreme cold past −45 °C wind chill is the most common closure trigger.
Blizzard warnings drive closures; −45 °C is operational.
Blizzard warnings only; cold alone rarely closes school.
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