Historical Snow Day Trends: What the Data Shows

📅 November 28, 2025 ✍️ Data Team ⏱️ 3 min read

Is it just us, or are snow days getting rarer? Or maybe more frequent? We dove into the last decade of closure data for the Halton District School Board (HDSB) to separate myth from fact.

The "Ice Storm" Effect

The 2017-2018 winter season was an outlier. An unprecedented ice storm in April led to multiple closure days. Since then, HDSB and other boards have adopted a slightly more cautious approach, especially when freezing rain is forecasted.

                Stat: Freezing rain causes closures 3x more often than snow alone. It's the "silent
                killer" of school days because it makes bus travel impossible.
            

Which Month Has the Most Snow Days?

You might think January, the coldest month, takes the crown. But our data reveals a surprise:

February: 45% of all snow days
January: 30% of all snow days
December: 15% of all snow days
March/April: 10% (mostly ice storms)

February is historically the snowiest and most volatile month in Southern Ontario, leading to the highest probability of cancellations.

The Shift in 2024

In recent years, we've noticed a shift towards system-wide closures rather than just bus cancellations. In the past, schools would often remain "open" even if buses were cancelled. Now, for safety and equity reasons, if buses aren't running in all zones, it's increasingly common for the entire system to shut down.

Using History to Predict the Future

Our Snow Day Predictor algorithm weighs this historical data heavily. If we see a forecast for 15cm of snow in mid-February with a temperature drop, our model knows (based on 2019 and 2021 data) that there is a >80% chance of closure.

Don't guess—use data. Check today's probability now.