From Academic Kids
Because the factors involving classification of winter storms are complex, there are many different definitions of blizzard. A major consensus is that in order to be classified as a blizzard, as opposed to merely a winter storm, the weather must meet several conditions. The storm must decrease visibility to a quarter of a mile for three consecutive hours, include snow or ice as precipitation, and have wind speeds of at least 32 mph (seven or more on the Beaufort Wind Scale).
Another standard, according to Environment Canada, is that the winter storm must have winds of 40 km/h or more, have snow or blowing snow, visibility less than 1 km, a wind chill of less than -25 degrees Celsius, and all of these conditions must last for 4 hours or more, before the storm can be properly called a blizzard.
When all of these conditions persist after snow has stopped falling, meteorologists refer to the storm as a ground blizzard.
Severe blizzards can occur in conjunction with arctic cyclones.
An extreme form of blizzard is a whiteout, when downdrafts coupled with snowfall become so severe that it is impossible to distinguish the ground from the air. People caught in a whiteout can quickly become disoriented, losing their sense of direction.
The word blizzard is of unknown origin, but may originate from the surname Blizzard. It was first widely used after the great American winter storm now known as the "Blizzard of 1880."  (http://www.etymonline.com/index.php?search=blizzard)
Certain types of blizzards in the northeastern United States are colloquially known as Nor'easters.
Famous U.S. Blizzards
There have been many devastating blizzards throughout U.S. History.
It is not uncommon for a region of the United States or North America to be struck by two devastating winter storms in one season. The Blizzard of 1888 paralyzed the Northeastern United States. In this 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.
These unpredictable storms can come without much warning, causing damage and destruction to humans and infrastructure. The Armistice Day Blizzard in 1940 caught many people off guard with its rapid and extreme temperature change. It was 60 degrees Fahrenheit 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.
One-hundred five years to the day (March 12) after the 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 entire winter. Highways and airports were closed across the U.S. As a wider effect, the storm spawned 15 tornadoes in Florida. When the Storm of the Century was over, it affected at least half the of U.S. population; 270 people died and 48 were reported missing at sea.