Cornwall Snow Day Predictor – Upper Canada DSB and Catholic DSB of Eastern Ontario
Will Tomorrow Be a Snow Day?
Canada's most accurate snow day predictor
Cornwall sits on the St. Lawrence River in the far eastern corner of Ontario, near the Quebec and New York borders. The city averages approximately 200–240 cm of snow per year – comparable to Ottawa – driven by St. Lawrence Valley storm systems and Alberta Clippers tracking through eastern Ontario. Cornwall is served by the Upper Canada District School Board (UCDSB), whose extensive rural eastern-Ontario territory makes rural bus route safety a central closure factor.
Will Cornwall schools be closed tomorrow? Enter your city in the predictor above for tonight’s closure probability, updated hourly from Environment Canada data. Always confirm with your school board’s official channels before making plans.
Cornwall School Boards – Who Decides Closures
- Upper Canada District School Board (UCDSB) – Cornwall, Brockville, and eastern Ontario counties (SDG, Leeds-Grenville). ucdsb.on.ca | Announces: by 6:00 AM | Radio: Corus Cornwall, Fresh Radio | Twitter/X: @UCDSB
- Catholic District School Board of Eastern Ontario (CDSBEO) – Catholic board for eastern Ontario. cdsbeo.on.ca | Announces: by 6:00 AM | Twitter/X: @CDSBEO
- Conseil scolaire de district catholique de l’Est ontarien (CSDCEO) – French Catholic board serving Cornwall and eastern Ontario.
Cornwall Snow Day Triggers – What Closes Schools Here
Cornwall’s closures are driven by:
- St. Lawrence Valley storms: Cornwall’s position in the St. Lawrence Valley exposes it to storm systems tracking up the valley, often bringing heavy snow and mixed precipitation.
- Alberta Clippers: Fast-moving northern systems track through eastern Ontario, delivering quick, intense snowfalls to the Cornwall area.
- Rural eastern-Ontario drifting: The UCDSB serves extensive rural territory across Stormont, Dundas, and Glengarry counties where open roads drift heavily.
- Freezing rain: Cornwall’s eastern position means it frequently experiences freezing rain events on the rain/snow line.
How Often Do Cornwall Schools Close?
The Upper Canada DSB’s Cornwall-area schools close approximately 5–8 days per year – comparable to Ottawa – with rural SDG county bus cancellations more frequent. December through February are peak months.
See Also – Nearby Predictors and Guides
Explore the Ontario Snow Day Predictor for all school boards in the province, or check nearby cities:
Related guides:
Frequently Asked Questions – Cornwall Snow Days
Which school board and bus system does the Cornwall predictor track?
The predictor calculates data for the Upper Canada District School Board (UCDSB) and the Catholic District School Board of Eastern Ontario (CDSBEO). The official transit authority it simulates is the Student Transportation of Eastern Ontario (STEO).
Why does the Cornwall predictor show a high percentage when city streets are clear?
Cornwall sits within a massive regional transport boundary that includes expansive rural areas across Stormont, Dundas, and Glengarry (SD&G). The predictor calculates risk for the entire zone, meaning that blinding snow, heavy drifts, or black ice on open rural county roads outside town limits will cancel buses for Cornwall schools even if downtown streets are clear.
How much snow is required to trigger a high percentage on the Cornwall predictor?
Because Eastern Ontario is well-equipped for winter, standard snowfall rarely triggers a cancellation. The predictor’s algorithm spikes sharply when a weather warning forecasts 15 to 20 cm of rapid accumulation right before the morning commute, or when severe freezing rain warnings threaten to glaze major corridors like Highway 401.
If the Cornwall predictor hits 100% and buses are called off, do schools close?
No, schools almost always stay open for walking students and staff even when buses are cancelled. However, a maximum predictor percentage helps parents prepare for “inclement weather days” where regular curriculum delivery is officially paused, and all scheduled tests, exams, or presentations are postponed.
What time is the Cornwall snow day predictor most accurate?
The morning check between 5:00 AM and 5:30 AM is the most accurate window. While checking at 9:00 PM the night before provides a helpful baseline estimate, volatile winter storm tracks moving up the St. Lawrence Valley can shift rapidly overnight, requiring final morning radar updates right before the official STEO announcement at 6:15 AM.