Eastern Ontario
Ottawa is colder and snowier than Toronto with no lake to soften a storm, and freezing rain is a recurring valley problem. The estimate below is loaded with live Ottawa forecast data.
Live Ottawa forecast estimate
Enter a location to compare tomorrow's snow, ice, temperature, wind and morning timing.
Local conditions
Ottawa sits inland in eastern Ontario where the Ottawa Valley meets the St. Lawrence lowlands, far from any moderating body of water. Overnight temperatures fall further than in southern Ontario, so precipitation is more reliably frozen and refreeze is dependable. The valley geography also traps cold air at the surface while milder air arrives aloft from the south, which is the classic freezing-rain arrangement. That makes Ottawa's most disruptive winter events a mix of deep, cold snowfall and periodic icing rather than the marginal slush that characterises the lakeshore cities.
What actually drives a decision
Ice events here disrupt transportation with very little measurable accumulation because a glaze cannot be plowed. Read whether the snow-and-ice factor cites an icing signal, and check the temperature minimum against the forecast rain amount rather than looking only at snowfall.
Ottawa student transportation is coordinated across boards and cancellations are announced by zone, with rural zones frequently cancelled while urban zones run. That means the practical question on a bad morning is which zone a school sits in, not whether the whole city has closed.
Because Ottawa winters run genuinely cold, snow and ice persist on secondary streets and sidewalks between events rather than melting away. A later modest snowfall lands on an already compromised surface, and wind chill at a bus stop becomes a safety consideration in its own right.
Ottawa's boundaries include substantial rural territory with long, exposed roads. Drifting and reduced visibility on those routes can force transportation cancellations under a clear sky, hours after snowfall has ended.
The forecast for the coordinates above is scored against six weighted factors: snow and ice, temperature, wind chill, morning timing, area and routes, and school level. Around Ottawa the rows that most often carry the number are snow and ice, temperature, wind chill. Every factor appears in the result with its own value, score bar and published weight, so a percentage is never presented without the reasoning behind it. The methodology page documents each threshold, and the accuracy and limitations page sets out what the model cannot observe.
This site does not publish closure thresholds for any school system, because those are operational judgements rather than published numbers. What it can do is point you at the organisations that actually decide. Around Ottawa, ON those include:
Treat the estimate on this page as a reason to prepare and to keep checking, never as an announcement. A school system can close buildings, delay the start, cancel transportation only, dismiss early or move to a different learning format, and those outcomes are not interchangeable.
Primary sources for weather warnings and road conditions covering Ottawa. School decisions still come from the systems listed above.
Ottawa questions
This page estimates weather pressure only. Ottawa's boards announce closures while the regional transportation service announces cancellations by zone, so a rural zone can lose its buses on a morning when urban routes run normally. Find the zone covering the school.
Toronto sits beside a large lake that keeps its surface air relatively well mixed. Ottawa sits inland where cold air settles into low ground and stays there, so when milder air arrives overhead there is a persistent sub-freezing layer for rain to fall into. Distance from the lakes accounts for most of the difference.
Transportation is cancelled for specific geographic zones rather than for a whole board, so rural routes can be cancelled while urban routes operate. Check which zone the school is in before assuming buses are or are not running.
No. It raises an icing signal from the forecast when rain is expected at or below freezing, but it does not predict ice thickness. Environment and Climate Change Canada publishes expected ice accretion in its freezing rain warnings, and for an Ottawa ice event that figure is the one to read.
Still deciding what to do with the number? Read how schools make the final call and the guide to the best times to check a forecast.