Southwestern Ontario
London sits in the snowbelt between Lake Huron and Lake Erie, where squalls off Huron are the defining winter hazard. The estimate below is loaded with live London, Ontario forecast data.
Live London forecast estimate
Enter a location to compare tomorrow's snow, ice, temperature, wind and morning timing.
Local conditions
London occupies the middle of southwestern Ontario's peninsula, close enough to Lake Huron that northwest flow drives snow squall bands directly over the city. Because those bands form over open water and organise as they travel inland, London can experience intense, localised snowfall with sharp visibility loss while communities to the east stay clear. The surrounding Thames Valley countryside is farmland with long, exposed roads, and the local school boards operate one of the largest rural bus networks in the province, which is why transportation cancellations here are far more common than closures.
What actually drives a decision
Squall bands are narrow, intense and fast. Visibility can collapse within minutes and accumulation rates can outpace plowing while the band sits over one area. Environment and Climate Change Canada snow squall watches and warnings are the products to read here, not a daily snowfall figure.
The Thames Valley board covers extensive rural territory beyond the city, and transportation is cancelled by zone. Rural zones are frequently cancelled while London city routes operate. Schools generally stay open with staff on site, so the zone status is the practical answer on a bad morning.
Wind lifts existing snow across straight, unsheltered county roads and rebuilds drifts after plowing. A route can be impassable under a clear sky, and visibility on those roads is a genuine safety concern for buses.
Sitting between Huron and Erie, London can see precipitation type shift within a single event. Read the temperature factor alongside snowfall, and note whether the snow-and-ice factor cites an icing signal rather than accumulation.
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 London the rows that most often carry the number are snow and ice, area and routes. 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 London, 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 London. School decisions still come from the systems listed above.
London questions
This page estimates weather pressure only. The Thames Valley and London District Catholic boards announce closures, and transportation is cancelled by zone, with rural zones affected far more often than routes inside the city itself.
Northwest winds cross the open water of Lake Huron and form narrow, intense snow bands that travel southeast directly over southwestern Ontario. London's position in the peninsula puts it in that path repeatedly through the winter.
Transportation is cancelled by geographic zone, and rural zones are commonly cancelled while city routes operate. Confirm which zone the school falls into rather than assuming a single answer for the whole board.
Because the decision covers a whole zone rather than the city centre. A squall band or drifting on exposed county roads outside London can make rural routes unsafe while downtown streets are dry, and the cancellation follows the worst conditions on the route rather than the best.
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.