Six Cold Snaps That Hit Several Canadian Cities

By Julia · weather-canada.com editorial team · Published 23 October 2026 · 5 min read

When news reports say the "polar vortex" has arrived, they are describing a cold outbreak, not a rare object. The vortex itself is a ring of strong winds that circles the pole every winter. Whether a given outbreak was tied to that ring weakening or stretching is a question for atmospheric scientists with upper-air data, and ten points on the ground cannot answer it. What daily temperatures can do is count: how often, where, how deep, and for how long. So this article skips the label and applies one rule to the data.

The rule

A cold snap, here, is a run of at least three days in a row between November and March when the daily mean temperature is 12 degrees or more below that day's normal. The normal is the 1991–2020 monthly normal printed on this site, interpolated between mid-months. The temperatures are ERA5 reanalysis values for 2016–2025 at the centre of six cities: Toronto, Montréal, Ottawa, Winnipeg, Calgary and Edmonton. Overlapping runs, within two days of each other, are merged into one outbreak.

The rule found 62 city-level runs. Calgary had 28 of them, Edmonton 24 and Winnipeg 8; Montréal and Ottawa had one each, and Toronto none. That lopsided score is the first result: by this yardstick, a cold snap is a prairie phenomenon, and an uncommon one in the east.

Six outbreaks that hit three cities or more

December 6–18, 2016. Winnipeg, Calgary and Edmonton. Calgary's run lasted eight days, from December 6 to 13, with daily means averaging −20.8 °C. The lowest minimum of the outbreak, −35.1 °C, came in Winnipeg between December 15 and 18.

December 25, 2017 to January 2, 2018. The only outbreak that crossed the country. Calgary and Edmonton saw seven days each, Calgary at a daily mean 26.0 degrees below normal at its worst. Two days later Ottawa and Montréal met the rule too, Ottawa until January 1 and Montréal until January 2: Montréal's lowest minimum was −29.3 °C and Ottawa's −31.1 °C. Toronto stayed just outside the rule, but at a looser threshold of 10 degrees below normal it counts three days, December 26 to 28, with a low of −24.8 °C.

January 29 to February 15, 2019. Winnipeg had three days from January 29 to 31, and its lowest night of the decade fell in them: −38.0 °C on January 30. Edmonton's run was the longest in the data, 14 days from February 2 to 15, with a lowest minimum of −39.6 °C. Calgary was in it too.

February 5 to 15, 2021. Calgary took ten days, from February 6 to 15, at a mean of −26.1 °C. Edmonton reached −41.0 °C; Winnipeg joined from February 11 to 14. Further north, Yellowknife's coldest night of the decade, −45.2 °C, came on February 7 of the same spell.

December 24, 2021 to January 8, 2022. Calgary's six days, December 24 to 29, were the coldest in terms of gap to normal for any single run in this period, 26.9 degrees below the seasonal figure on the worst day. Edmonton's run lasted nine days and ended on January 1. Winnipeg's started on December 29 and ran five days, to January 2.

February 12 to 19, 2025. The most recent of the six. Edmonton had eight days, Calgary six, and Winnipeg three from February 16 to 18; the lowest minimum was −33.4 °C.

One outbreak is missing because it involved only two cities: January 10 to 15, 2024, when Calgary hit −39.4 °C on January 14, its decade low, and Edmonton ran six days in a row, January 10 to 15, with a deepest daily gap of 24.1 degrees below normal.

The pattern: the prairies keep the cold

Count the winter days that were at least 12 degrees colder than normal and the same hierarchy shows up. Calgary logged between 7 and 19 per winter. Edmonton ranged from 6 days in 2023–24 to 22 in 2021–22. Winnipeg was more erratic, from 0 days in 2023–24 to 15 in 2021–22. Toronto never had more than six in a winter, and in six of the nine winters, none at all.

Two lessons follow. The first is that a hard cold week is the rule in a prairie winter, not the exception: every winter in the series gave Calgary at least seven such days and Edmonton at least six. The second is how uneven the rest is. Winnipeg went from 15 cold days in 2021–22 to none in 2023–24, so a quiet winter in one city says little about the next one.

What to do with that

The practical reading is about planning, not prediction. A cold snap on the prairies can last a week or more (Edmonton's longest run in the data was 14 days), so a car, a house or a trip should be prepared for a block of cold, not one bad night: block heater plugged in, a full tank, a warm layer in the trunk. And when the same spell reaches Ottawa and Montréal, it does so for about a week, with minima between −29 and −31 °C. For what that cold feels like with wind, read wind chill in numbers. For the opposite swing, the warm days that interrupt prairie winters, see Chinook and prairie winters.

Period of the data cited: 2016–2025.