What Defines a Blizzard?

Every year dozens of winter storms impact the United States with rain, ice snow, and wind; however, what separates a run-of-the-mill storm from a blizzard? The term "blizzard" refers to a violent winter storm characterized by snow, strong winds, and low temperatures. Specifically, a storm is coined a blizzard when winds of 35 mph or higher along with visibilities of 1/4 mile or less are expected for three hours or longer.

In the United States, Blizzards can occur in almost any area that is cold enough for snow; however, an article published in the Journal of Climate found that blizzards occur most frequently over the northern Plains as well as parts of the Rockies and the Sierras of California.

Blizzards are not unique to the U.S. and North America. In fact, these powerful storms have been known to be a deadly phenomenon for several parts of the world. The deadliest blizzard on record across the globe killed around 4,000 people in Iran in 1972. Parts of that country were buried under 10 feet of snow over the span of 7 days with even larger snow drifts.

Interestingly enough, snow does not have to be falling from a cloud in order to have a blizzard. A "ground blizzard" is a term given when strong winds over a region pick up snow that is already on the ground and blow it around severely reducing visibility. If wind speeds of over 45 mph are recorded for three or more hours along with heavy snow and temperatures below 10 degrees Fahrenheit, the storm can be considered a “severe blizzard”.

While a majority of winter storms don’t meet the criteria to qualify as a blizzard, those storms in which blizzard conditions are present certainly need to be taken seriously.