Blizzards can bring whiteout conditions, and can paralyze regions for days at a time, particularly where snowfall is unusual or rare.Ī severe blizzard has winds over 72 km/h (45 mph), near zero visibility, and temperatures of −12 ☌ (10 ☏) or lower. While severe cold and large amounts of drifting snow may accompany blizzards, they are not required. Ī view of Jätkäsaari, Helsinki, Finland, during a brief but intense blizzard on a March evening. These conditions must persist for a period of at least four hours for the storm to be classified as a blizzard, except north of the arctic tree line, where that threshold is raised to six hours. Įnvironment Canada defines a blizzard as a storm with wind speeds exceeding 40 km/h (25 mph) accompanied by visibility of 400 metres (0.25 mi) or less, resulting from snowfall, blowing snow, or a combination of the two. To be a blizzard, a snow storm must have sustained winds or frequent gusts that are greater than or equal to 56 km/h (35 mph) with blowing or drifting snow which reduces visibility to 400 m or 0.25 mi or less and must last for a prolonged period of time-typically three hours or more. The difference between a blizzard and a snowstorm is the strength of the wind, not the amount of snow.
In the United States, the National Weather Service defines a blizzard as a severe snow storm characterized by strong winds causing blowing snow that results in low visibilities.
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