According to Environment Canada, a winter storm must have winds of 40 km/h (25 mph) or more, have snow or blowing snow, visibility less than 1 km (about 5⁄8 mile), a wind chill of less than −25 °C (−13 °F), and that all of these conditions must last for 4 hours or more before the storm can be properly called a blizzard.
In the United States, the National Weather Service defines a blizzard as sustained 35 mph (56 km/h) winds which lead to blowing snow and cause visibilities of ¼ mile or less, lasting for at least 3 hours. Temperature is not taken into consideration when issuing a blizzard warning, but the nature of these storms is such that cold air is often present when the other criteria are met.
Other countries, such as the UK, have a lower threshold: the Met Office defines a blizzard as "moderate or heavy snow" combined with a mean wind speed of 30 mph (48 km/h) and visibility below 650 feet (200 m).
When there are blizzard conditions but no snow falling, meteorologists call this a ground blizzard because all the snow is already present at the surface of the earth and is simply being blown by high winds. Ground blizzards require large expanses of open and relatively flat land with a sufficient amount of accumulated and loosely packed, powdery snow to be blown around.
The Great Blizzard of 1888 paralyzed the Northeastern United States for several days. In that blizzard, 400 people were killed, 200 ships were sunk, and snowdrifts towered 15 to 50 feet high. Earlier that year, the Great Plains states were struck by the Schoolhouse Blizzard that left children trapped in schoolhouses and killed 235 people.
The Midwestern Armistice Day Blizzard in 1940 caught many people off guard with its rapid and extreme temperature change. It was 60 °F in the morning, but by noon, it was snowing heavily. Some of those caught unprepared died by freezing to death in the snow and some while trapped in their cars. Altogether, 154 people died in the Armistice Day Blizzard. Unpredictable storms such as this one can come without much warning, causing damage and destruction to humans and infrastructure.
One hundred five years March 12 after the Great Blizzard of 1888, a massive blizzard, nicknamed the Storm of the Century, hit the U.S in 1993. It dropped snow over 26 states and reached as far north as Canada and as far south as Mexico. In many southern U.S. areas, such as parts of Alabama, more snow fell in this storm than ever fell in an averagely recorded in any winter yet. Highways and airports were closed across the United States Of America. As a wider effect, the storm spawned 15 tornadoes in Florida. When the storm was over, it affected at least quarter of the U.S. population; 270 people died and 48 were reported presumed dead at sea.