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A significant winter storm is set to impact Southern Ontario beginning Wednesday afternoon, lasting through the night, and continuing into Thursday morning.

Environment Canada has issued widespread winter storm warnings, snowfall warnings, and freezing rain warnings across the region, signalling the potential for hazardous conditions.

With snowfall totals expected to range between 20 and 40 cm by Thursday morning across Southwestern, Central, and Eastern Ontario, road conditions will likely be extremely treacherous.

Snowfall rates could exceed 5 cm per hour at times, making it difficult for snowplows to keep up. Even though the most intense conditions will occur Wednesday evening into the early overnight hours, the aftermath will still pose significant challenges for travel.

Given the severity of this storm, there is a very high likelihood that school buses will be cancelled across most of Southern Ontario. In fact, the probability of widespread bus cancellations across Southwestern, Central, and Eastern Ontario is over 90%.

School closures are also a strong possibility, particularly with Environment Canada's warnings emphasizing the dangers of travel on Thursday morning. Some school boards may even choose to announce cancellations proactively tonight. We will update this article if any school boards confirm closures in advance.

In the Golden Horseshoe and Niagara region, school boards tend to be more cautious when it comes to bus cancellations and school closures, as urban areas typically have better snow-clearing operations. However, there is also a chance of mixed precipitation in these regions, which could lower snowfall totals to around 10-20 cm.

This uncertainty makes cancellations less of a guarantee compared to other parts of the province. As a result, we’ve placed the likelihood of school bus cancellations at around 75% for Halton (South), Peel (South), York, Durham (South), and KPR (Clarington).

Meanwhile, for Toronto, Hamilton, and Niagara, it’s a 50/50 call and could go either way depending on how the storm unfolds overnight.

Deep Southwestern Ontario, including Windsor, Chatham, Sarnia, and London, also has a slightly lower probability of bus cancellations, sitting at around 75%. The system is expected to taper off earlier in these regions, and some areas could transition to rain by morning.

If that happens, conditions might improve enough for buses to operate. However, given the ongoing warnings from Environment Canada, school boards in these areas may still err on the side of caution and cancel transportation regardless.

Stay tuned for updates as the storm progresses, and check back for confirmation from school boards on closures and cancellations tonight and Thursday morning.

Disclaimer: Instant Weather has zero authority when it comes to bus and school closures.

It is completely up to the school boards, bus companies, local authorities, and parents to decide what is best for their children. This is our best guess based on our forecast.