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Pockets of heavy lake-effect snow accompanied by localized snow squalls are expected to develop tonight across areas near Lake Huron, Georgian Bay, and Lake Ontario.

These conditions are likely to result in notable snowfall accumulations ranging from 10 to 20 cm, as well as near-zero visibility throughout much of Thursday morning and afternoon.

Environment Canada has issued a range of advisories, watches, and warnings across these regions, reflecting the potentially hazardous conditions. With this in mind, school boards in some of the hardest-hit areas may choose to cancel school buses on Thursday morning.

The highest likelihood of cancellations is in the Sudbury, Manitoulin Island, and Bruce Peninsula regions, where snow squall warnings are currently in effect. These areas are expected to experience the most intense snowfall and the worst visibility.

Elsewhere, locally heavy lake-effect snow could develop along the Lake Huron shoreline. Environment Canada has issued a weather advisory for this region, highlighting the possibility of impactful snow.

Meanwhile, a snow squall watch has been issued for parts of the northern Lake Ontario shoreline, including areas from Oshawa to Colborne.

The impact of lake-effect snow in these advisory and watch zones remains uncertain, and conditions could vary significantly depending on the development and positioning of the squalls.

Given this uncertainty, we're assigning a 50% chance of school bus cancellations in these areas, as the decision could easily go either way.

Here is a breakdown of the likelihood of school bus cancellations by region:

Almost Certain (90% Chance)

Rainbow District School Board

Likely (75–90% Chance)

Bluewater District School Board (Bruce Peninsula)

Possible (50–75% Chance)

Bluewater District School Board (Kincardine and Southampton)
Avon Maitland District School Board (Goderich)
Near North District School Board (Town of Parry Sound)
Kawartha Pine Ridge District School Board (Clarington and Northumberland)

Maybe (25–50% Chance)

Avon Maitland District School Board (Listowel and Exeter)
Bluewater District School Board (Hanover and Owen Sound)
Near North District School Board (East Parry Sound and North Bay)
Durham District School Board (Oshawa)
Algoma District School Board

Unlikely (10–25% Chance)

Avon Maitland District School Board (Stratford)
Thames Valley District School Board (Middlesex)
Bluewater District School Board (Meaford)
Trillium Lakelands District School Board (Muskoka and South CKL)
Durham District School Board (North)
Kawartha Pine Ridge District School Board (Peterborough)
Tri-Board (Belleville and Prince Edward County)

For the rest of Southern Ontario, the chance of school bus cancellations on Monday is less than 10%.

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.