Ottawa Snow Day Predictor & Calculator
Will OCDSB or OCSB close tomorrow?
Ottawa averages 8 to 10 school closure days per year — nearly double Toronto despite a similar annual snowfall total of 235cm. The reason is not snowfall volume. It is ice storms. When Atlantic moisture overrides Arctic air trapped in the Ottawa Valley, precipitation falls as freezing rain rather than snow. Five millimetres of ice on rural Ottawa roads closes schools that 30cm of snow would not.
snowdayprediction.ca reads live Environment Canada weather data and applies OCDSB's documented closure behaviour to give you a snow day predictor & calculator probability score hours before the 6:00 AM announcement. The Ottawa-Carleton District School Board snow day threshold is driven by rural route conditions — not urban road conditions. Check at 9pm the night before for your best early read.
OCDSB Announcement Window
By 6:00 AM
Check at 9pm the night before for an early read — especially if a freezing rain warning has been issued. Check again at 5am for the final pre-announcement probability before OCDSB announces by 6:00 AM.
Ottawa School Boards — OCDSB & OCSB
Two school boards serve Ottawa — both make independent closure decisions and almost always align. Rural route conditions drive both boards' thresholds.
Ottawa-Carleton District School Board
OCDSB covers Ottawa's entire urban and rural area — from Centretown and the Glebe to Osgoode, Richmond, Metcalfe, and Greely. Rural route conditions in these outlying communities, not urban road conditions, drive the closure decision. One impassable rural route is enough to close all 150 schools.
Ottawa Catholic School Board
OCSB almost always aligns with OCDSB — both boards monitor the same road condition reports from School Bus Ottawa and typically announce within minutes of each other. Always verify at ocsb.ca or @OttCatholicSB directly rather than assuming OCDSB's decision applies.
OCDSB covers all of Ottawa: If you live in Kanata, Orleans, Barrhaven, Nepean, Gloucester, Vanier, or rural communities including Osgoode, Richmond, Metcalfe, and Greely — the Ottawa snow day predictor applies to your school. All 150 OCDSB schools close simultaneously when a closure is called.
Verify Here When the Announcement Drops
Always verify from official sources — predictions update hourly but announcements are final.
Ottawa Bus Cancellation — OC Transpo vs School Bus Ottawa
Ottawa has two separate bus systems. One almost never cancels. The other cancels frequently. Know which one your child uses.
OC Transpo Almost Never Cancels
OC Transpo — Ottawa's urban transit system — operates through virtually all winter weather events. Like the TTC in Toronto, OC Transpo is designed for year-round urban operation. An OCDSB school closure does not mean OC Transpo is disrupted. Families in Centretown, the Glebe, Sandy Hill, and other walkable urban neighbourhoods who rely on OC Transpo to get children to school are not affected by bus cancellations — they are only affected by the school closure decision itself.
School Bus Ottawa Cancels Frequently
School Bus Ottawa operates the dedicated school bus routes across Ottawa — including rural routes to Osgoode, Richmond, Metcalfe, and outlying communities. These routes cancel far more frequently than OC Transpo during winter storms. A School Bus Ottawa cancellation often precedes a full OCDSB closure decision — if School Bus Ottawa cancels, prepare for a full school closure but verify at ocdsb.ca. Check schoolbusottawa.ca for route-specific cancellation status.
Bottom line for Ottawa families: If your child takes OC Transpo — watch for the school closure decision only. If your child takes School Bus Ottawa — check schoolbusottawa.ca AND ocdsb.ca separately. These are two different announcements.
Ottawa Snow Day Patterns — Ice Storms & Rural Routes
Why Ottawa closes schools more than Toronto — and why freezing rain, not snowfall, is the real closure trigger.
Freezing Rain Is the Real Closure Trigger
Ottawa sits in a valley convergence zone where cold Arctic air meets milder, moisture-laden systems tracking up the St. Lawrence valley. When warm Atlantic air overrides Arctic cold trapped in the Ottawa Valley, precipitation falls as freezing rain rather than snow. These ice storms are often forecast as rain but arrive as ice — catching families off guard. A freezing rain event depositing 5 to 8mm on rural Ottawa roads creates conditions far more dangerous than 20cm of snow, and OCDSB responds accordingly. Environment Canada freezing rain warnings issued after 8pm are your strongest signal for a next-morning closure.
Rural Ottawa Freezes Harder Than the Urban Core
OCDSB's geographic footprint is vast — stretching from urban Centretown to rural communities in Osgoode, Richmond, and Metcalfe where roads receive lower plowing priority and freezing rain accumulates faster. A storm that leaves the Queensway drivable can make County Road 8 in Osgoode completely impassable. OCDSB makes a single closure decision for all 150 schools — rural route conditions, not urban conditions, set the threshold. This is why Ottawa closes at lower snowfall totals than you would expect based on how the urban core looks.
Highway 417 — The Key Road Corridor
Highway 417 — the Queensway — is Ottawa's primary road corridor and the route monitored by OCDSB transportation assessors from 3am on storm mornings. Ice on the Queensway is a serious closure signal but not sufficient on its own — OCDSB also monitors rural county roads. Check 511on.ca for live Highway 417 conditions. If the Queensway is showing ice warnings alongside rural road closures, a full OCDSB closure is very likely.
Ottawa vs Ontario — School Closure Comparison
Ottawa averages 8 to 10 school closure days per year — nearly double Toronto's 3 to 5 days despite a similar annual snowfall total of 235cm. The difference is entirely explained by rural routes and ice storms. Ottawa also closes more than Hamilton (6 to 8 days) and Kitchener (5 to 7 days) because of its larger rural footprint and higher ice storm frequency in the Ottawa Valley corridor.
What to watch for in Ottawa: A freezing rain warning issued by Environment Canada after 8pm is your strongest signal for an OCDSB closure — stronger than any snowfall forecast. Snowfall alone rarely closes Ottawa schools unless it exceeds 20cm overnight on top of existing poor road conditions. Check snowdayprediction.ca at 9pm and again at 5am for the most accurate reads.
Ottawa OCDSB Snow Day History
Historical OCDSB closure data — what storms actually closed Ottawa schools and why.
Notable OCDSB Closure Events
The last major OCDSB closure was February 23, 2023, when a St. Lawrence valley ice storm deposited 15mm of freezing rain across Ottawa overnight. OCDSB typically closes when overnight freezing rain exceeds 5mm on rural routes, or when snowfall exceeds 20cm with persistent northwest winds.
St. Lawrence valley ice storm deposited 15mm of freezing rain. OCDSB and OCSB both closed. Queensway reduced to two lanes. Power outages in Kanata and Barrhaven.
Alberta clipper deposited 28cm across Ottawa in 18 hours. OCDSB closed. Rural routes in Osgoode and Richmond declared impassable by 4am — urban core roads were manageable.
8mm of freezing rain on rural Ottawa roads. OCDSB closed while OC Transpo continued normal service in the urban core — a clear illustration of how rural routes drive the decision.
Worst Ottawa winters on record for school closures
2007–2008 · 2013–2014 · 2019–2020 — these winters produced the highest number of closure events, with 2013–2014 recording multiple consecutive closure days during the worst ice storm season in recent Ottawa history.
Last Notable Ottawa Storm Event
OCDSB and OCSB both closed. 15mm of freezing rain across Ottawa — Queensway reduced to two lanes, power outages in Kanata and Barrhaven. A textbook St. Lawrence valley ice storm closure.
Tracking Ottawa closures since launch — this card updates after each recorded closure event.
Ottawa Road Conditions
Highway 417 (Queensway) · Highway 416 · County Road 8 · Rural Routes
Highway 417 conditions are monitored by OCDSB assessors from 3am on storm mornings — but rural county roads in Osgoode, Richmond, and Metcalfe are equally important. Check 511on.ca for live Ontario road conditions. If both the Queensway and rural routes show ice warnings simultaneously, an OCDSB closure is very likely.
What Do Ottawa Parents Think?
Will OCDSB close tomorrow? Cast your vote — resets daily at midnight.
Community vote — not a prediction. Check the probability gauge above for the algorithm-based forecast.
Ottawa Snow Day Tips for Parents
OCDSB-specific advice based on how Ottawa school closures actually work.
Watch for Freezing Rain — Not Snow
OCDSB closes for freezing rain more than snowfall. If the overnight forecast shows freezing rain — even a small amount — the closure probability jumps significantly. An Environment Canada freezing rain warning after 8pm is your strongest signal. Snowfall alone below 20cm rarely closes Ottawa schools.
Know Which Bus System Your Child Uses
OC Transpo almost never cancels. School Bus Ottawa cancels frequently. Check schoolbusottawa.ca for your specific route. If School Bus Ottawa cancels your route, prepare for a full closure — but verify at ocdsb.ca. These are two separate announcements on two separate websites.
CFRA 580 AM Is the Fastest Source
CFRA 580 AM and CBC Radio One 91.5 FM receive OCDSB notifications simultaneously with the board website. Radio announcements often reach Ottawa families faster than website checks during high-traffic storm mornings. Keep a radio or streaming app ready on storm mornings.
Check at 9pm and 5am
The 9pm check gives you the best early read — especially critical in Ottawa where ice storms often arrive overnight with little advance warning. The 5am check gives you the most accurate pre-announcement read just before OCDSB assessors report in. OCDSB announces by 6:00 AM.
Ottawa Region & Nearby Cities — Snow Day Predictor
Snow Day FAQ — Ottawa & OCDSB
Ottawa-specific questions about OCDSB and OCSB school closure decisions.
Does OCDSB close for ice storms?
Yes — ice storms are the most common closure trigger for Ottawa schools, more than heavy snowfall. When Environment Canada issues a freezing rain warning overnight, the probability of an OCDSB closure increases significantly. Even 5-8mm of ice accumulation on rural Ottawa roads can make bus routes impassable while urban roads remain drivable.
What time does OCDSB announce school closures?
OCDSB announces by 6:00 AM. The fastest sources are Twitter @OCDSB and ocdsb.ca. CFRA 580 AM and CBC Radio One 91.5 FM also broadcast closure announcements from 6:00 AM.
Does OCSB close when OCDSB closes?
Almost always. OCDSB and OCSB use the same road condition data and typically announce within minutes of each other. In rare marginal events one board may close while the other stays open. Always check your specific board — ocsb.ca or @OttCatholicSB on Twitter.
Why does Ottawa close schools more than Toronto despite similar snowfall?
OCDSB covers a much larger geographic area including rural communities like Osgoode, Richmond, and Metcalfe where road clearing is slower and freezing rain accumulates faster. Toronto's TDSB serves a compact urban area where 300+ plows can clear priority roads within hours. OCDSB cannot make that same calculation for its rural routes.
Do Kanata, Orleans, Barrhaven, and Nepean follow OCDSB closures?
Yes — Kanata, Orleans, Barrhaven, Nepean, Gloucester, and rural communities including Osgoode, Richmond, Metcalfe, and Greely all fall under OCDSB. When OCDSB closes, all 150 schools close simultaneously. The snowdayprediction.ca Ottawa Snow Day Predictor is calibrated to OCDSB and applies to all of these communities.
Does OC Transpo cancel service during Ottawa snow days?
OC Transpo almost never cancels service during winter weather events. An OCDSB school closure does not mean OC Transpo is disrupted. School Bus Ottawa — which operates rural routes — is a separate service that may cancel independently. Check schoolbusottawa.ca for your specific route status.