A blizzard is a severe winter storm characterized by sustained winds of 35 miles per hour (56 kilometers per hour) or greater. It features falling or blowing snow that reduces visibility to 0.25 miles (0.4 kilometers) or less. These conditions must persist for a minimum of three hours to be classified as a blizzard.
Essential Conditions for Blizzard Formation
Blizzards require a specific combination of atmospheric conditions to form. Cold air, with temperatures at or below freezing (0°C or 32°F), is necessary for snow to form and remain frozen.
A significant moisture source is another crucial component, enabling substantial snowfall. This moisture often originates from large bodies of water, like oceans or large lakes, or from an approaching storm system carrying humid air.
Strong winds are the third essential element. Sustained winds of at least 35 miles per hour (56 kilometers per hour) are required. These powerful winds lift existing snow from the ground or drive falling snow horizontally, creating whiteout conditions.
Global Blizzard Prevalence
Blizzards occur most frequently in specific regions where the necessary atmospheric conditions regularly converge. North America experiences blizzards across its Great Plains, Midwest, and Northeastern United States, along with significant portions of Canada. Cold air masses frequently descend from the Arctic, interacting with moisture from the Gulf of Mexico or the Atlantic Ocean.
Antarctica stands as the most blizzard-prone continent. Its extreme cold, constant high winds, and readily available surface snow create an environment where blizzards are a near-daily occurrence. These storms are often driven by katabatic winds, which are dense, cold air currents flowing downhill from the high interior plateau to the coast.
Northern Eurasia, encompassing parts of Russia, Eastern Europe, and Central Asia, also sees frequent blizzard activity. Here, frigid continental air masses interact with moisture-laden systems. Mountainous regions worldwide, such as the Himalayas and Andes, can also experience blizzards due to orographic lift enhancing snowfall in conjunction with strong winds.
Factors Influencing Regional Blizzard Severity
Topography plays a role, as mountain ranges can channel and accelerate winds. Mountains also enhance snowfall through orographic lift, forcing moist air upwards.
Proximity to moisture sources impacts blizzard severity. Large freshwater bodies, like the Great Lakes in North America, generate “lake-effect” blizzards. Cold air masses moving over warmer lake waters pick up moisture and energy, leading to localized but intense snowfall downwind. Similarly, coastal areas near oceans can experience heavier blizzards when cold air interacts with oceanic moisture.
The regularity and intensity of cold air outbreaks from polar regions also influence blizzard severity. When cold air masses plunge southward, they create a steep temperature gradient, which can fuel more powerful storm systems. These outbreaks provide the deep cold necessary for widespread snow and strong winds. The typical paths that major winter storm systems follow, known as storm tracks, determine which regions are most frequently impacted by severe blizzards.