Southern Ontario: ‘Snow (Fog) Day’ Forecast for Thursday, March 5, 2026
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Thick fog is expected to redevelop across portions of Southwestern Ontario on Wednesday evening, with some of that fog potentially lingering into the early hours of Thursday morning.
This comes after dense fog led to widespread school bus cancellations across several rural school boards in the region on Wednesday morning. While the fog tonight does not appear to be as widespread or intense as last night, it may still be enough to cause visibility issues in some communities by Thursday morning.
Because of this, there remains the possibility that a few school boards could opt to cancel buses or delay service if visibility is significantly reduced during the early morning hours.
At this time, the most likely areas where a potential “fog day” could occur include Lambton County and Chatham-Kent under the Lambton Kent District School Board, Middlesex County under the Thames Valley District School Board, and all regions within the Avon Maitland District School Board.
These areas have historically shown a willingness to cancel buses when dense fog significantly reduces visibility along rural transportation routes. However, fog can be extremely difficult to forecast with precision. Conditions may be dense in one community while remaining relatively clear just a few kilometres away.
Because of this uncertainty, the highest probability we assign to fog-related cancellations is 25 percent. While cancellations are certainly possible in these regions, confidence is not high enough to suggest anything more widespread.
Elsewhere across Southwestern Ontario, we have assigned a low to very low chance of cancellations. Some patchy fog could still develop outside of the main fog-prone areas, but the likelihood of it becoming dense enough to trigger transportation decisions appears limited.
A similarly low probability extends into parts of Eastern Ontario along the northeastern shoreline of Lake Ontario. In particular, localized fog patches may develop near Kingston and surrounding rural communities under Tri-Board Student Transportation Services. However, the fog in this area is expected to be scattered and not widespread enough to pose a significant concern for school transportation.
Across the remainder of Southern Ontario, including the Golden Horseshoe, Central Ontario, and the Ottawa Valley, no impactful weather is expected during the school day on Thursday.
As a result, school bus cancellations are not expected in these regions, and most students across the province should be heading to school as usual.
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.
