Longueuil Snow Day Predictor — CSS Marie-Victorin School Closure Forecast

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Longueuil, Quebec Snow Day Predictor

Canada's most accurate snow day predictor

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Will Longueuil Schools Be Closed Tomorrow?

Longueuil is the main urban centre on the South Shore of the St. Lawrence River, directly across from Montreal. Part of the Greater Montreal metropolitan area, Longueuil is Quebec’s fourth-largest city and home to approximately 250,000 residents. While geographically integrated with Montreal, Longueuil sits in a distinct school authority structure — served primarily by the Centre de services scolaire Marie-Victorin (CSSMV) — and makes independent school closure decisions separate from Montreal’s CSSDM.

The South Shore’s winter weather is very similar to Montreal’s — Longueuil averages approximately 210–230 cm of snow per year — with some important differences. The South Shore is more exposed to winds from the south and southwest, and the lower-elevation terrain means fewer topographic barriers to slow approaching storms. Longueuil also lacks Montreal Island’s slight urban heat island effect.

School Authorities We Cover for Longueuil

  • Centre de services scolaire Marie-Victorin (CSSMV) — Primary French-language public school authority for Longueuil and surrounding South Shore communities including Brossard, Saint-Lambert, LeMoyne, Greenfield Park, and Saint-Hubert. csmv.qc.ca | Announces: by 6:30 AM | Radio: Radio-Canada Montréal, 98.5 FM | Twitter/X: @CSSMVictorin
  • Centre de services scolaire des Grandes Seigneuries (CSSDGS) — French-language board covering Longueuil’s western municipalities including La Prairie, Saint-Constant, Candiac, and Delson. csdgs.qc.ca
  • Sir Wilfrid Laurier School Board — English-language public board serving the South Shore including portions of Longueuil area. swlauriersb.qc.ca

South Shore vs. Montreal Island — Different Closure Dynamics

Despite being across a river from Montreal, the South Shore experiences meaningfully different snow day patterns. Montreal Island benefits from its island status — warmer overnight temperatures due to urban heat island effect and slightly milder conditions from the river surrounding it. The South Shore lacks this buffering: temperatures are consistently 1–3°C colder than Montreal overnight, precipitation is slightly more often snow than on the island, and bus routes cover more suburban and semi-rural terrain than central Montreal.

This means Longueuil and the South Shore school authorities sometimes close when Montreal’s CSSDM stays open, or implement delayed starts when Montreal opens normally. South Shore families should not assume that Montreal’s closure status determines their own board’s decision — they are independent authorities with different geographic coverage and different route conditions.

Longueuil Snow Day Statistics

CSSMV and surrounding South Shore school authorities average approximately 5–8 school closure days per year. Major storm events affecting greater Montreal affect the South Shore simultaneously, but borderline events produce independent decisions. South Shore closures trend slightly higher than Montreal’s CSSDM because of the colder temperatures and more extensive suburban bus route networks. January and February are peak months; March storms in Quebec can also be significant closure events.

When Does CSSMV Announce?

By 6:30 AM via csmv.qc.ca and Twitter/X @CSSMVictorin. Radio-Canada Montréal and 98.5 FM Montréal are the primary media channels. The CSSDGS and Sir Wilfrid Laurier School Board make independent announcements via their own channels. Quebec’s Education Ministry requires all CSS to communicate decisions by 6:30 AM at the latest on storm days.

Nearby Montreal-Area Communities

Frequently Asked Questions — Longueuil Snow Days

If Montreal closes, will Longueuil also close?

Not automatically. CSSMV, CSSDGS, and the Sir Wilfrid Laurier School Board all make independent closure decisions separate from Montreal’s CSSDM and EMSB. In major storm events that affect all of greater Montreal, closures typically align across all boards. In borderline events, South Shore boards may close while Montreal stays open (because South Shore is slightly colder and has more exposed bus routes), or vice versa. Always check your specific board’s website.

Why is Longueuil slightly colder than Montreal?

Montreal Island benefits from an urban heat island effect — the dense concentration of buildings, infrastructure, and human activity generates heat that raises surface temperatures by 1–3°C compared to surrounding areas. The South Shore’s less dense urban fabric and lack of island geography means it experiences the “true” regional temperature rather than Montreal’s slightly elevated island baseline. This small temperature difference can tip borderline precipitation events from rain to freezing rain or from freezing rain to snow in Longueuil when Montreal experiences a milder version of the same system.