Before the Sun Rises: How HDSB Decides to Close Schools

📅 January 15, 2026 ✍️ Snow Day Team ⏱️ 4 min read

Every winter morning, thousands of students in Oakville, Burlington, Milton, and Halton Hills wake up asking the same question: "Is it a snow day?"

But long before your alarm goes off, a dedicated team at Halton Student Transportation Services (HSTS) has been awake for hours, analyzing data to make that critical call. While it might seem random, the decision to close schools is based on a precise, time-sensitive protocol.

                Key Takeaway: The decision isn't just about snow accumulation. It's about safety, road
                conditions, and whether buses can run on time.
            

The 4:00 AM Wake-Up Call

The process begins at approximately 4:00 AM. While most of Halton Region is sleeping, HSTS staff begin reviewing:

Environment Canada Warnings: Checking for snowfall warnings, freezing rain, or extreme cold alerts.
Spotter Reports: HSTS has "spotters" across the region—real people who check road conditions in Zones 1, 2, and 3.
Municipal PLow Updates: contacting road crews in Oakville, Burlington, Milton, and Halton Hills to see if main arteries are cleared.

The Three Zones of Halton

Halton is huge. Weather in Oakville (Zone 1) near the lake can be totally different from Georgetown (Zone 3) near the escarpment. HSTS divides the region into three zones to make more targeted decisions:

Zone 1: Oakville and Burlington (South)
Zone 2: Milton (Central)
Zone 3: Halton Hills / Georgetown (North)

Often, you'll see "Buses Cancelled in Zone 3 only" while Zone 1 remains open. This keeps schools running where it's safe.

The 6:30 AM Deadline

A decision must be made by 6:00 AM to ensure it can be communicated to media and parents by 6:30 AM. Once the bus fleet is deployed, it's very difficult to recall them. That's why you rarely see a cancellation after 6:30 AM.

Does 10cm of Snow Close Schools?

Many students believe there's a magic number. Our historical analysis shows that HDSB has closed schools with as little as 10cm of snow if other conditions are bad (e.g., freezing rain or unplowed roads). However, we've also seen school stay open with 15cm if the roads were clear and the sun was out.

Want to know your odds for tomorrow? Check our Snow Day Predictor which uses this exact historical data to calculate your probability.