What Causes A Blizzard? (And How Is It Different From A Snow Storm?)

Hint: It has nothing to do with how much snow actually falls.

Winter blizzard
Man digging his car out of the snow during a blizzard. Getty Images

Every year, as the snow starts to fall, people start tossing around the word blizzard. It doesn't matter if the forecast is calling for one inch or one foot, it is suddenly referred to as a blizzard. But what exactly makes a snow storm a blizzard? And how is it different from your average winter weather? 

As is the case with most weather phenomenon, there are strict parameters that define what truly is a blizzard. In the U.S., the National Weather Service categorizes a blizzard as a severe snow storm with strong winds and blowing snow that limit visibility.

It's worth noting that the definition of a blizzard varies from country to country. Canada's Environment Canada defines a blizzard as a snow storm that lasts for at least three hours with winds blowing at or greater than 25 mph, accompanied by temperatures below -25˚C or -15˚F and visibility of less than 500 feet. In the United Kingdom, a blizzard is a storm that produces medium to heavy snowfall with winds of 30mph and visibility of 650 feet or less.

Thus, it's the strength of the wind that determines whether a storm is a blizzard or just a snow storm - not how much snow is dumped on a given area.

To put it in technical terms, in order for a snow storm to be characterized as a blizzard, it must winds that are blowing or gusting at speeds greater than or equal to 35 mph with blowing snow that reduces visibility to one-quarter mile or less. A blizzard also usually lasts for at least three hours.

Temperature and snow accumulation are not taken into account when determining whether or not a storm is a blizzard.

In fact, meteorologists are quick to point out that it doesn't always have to be snowing for a blizzard to occur. A ground blizzard is a weather condition where snow that has already fallen is blown around by strong winds, thereby reducing visibility. 

It is the winds of a blizzard - combined with the snow - that causes the most damage during a blizzard. Blizzards can paralyze communities, strand motorists, tear down power lines, and in other ways damage economies and threaten the health of those affected.

In the U.S. blizzards are most common in the Great Plains, the Great Lakes states, and in the Northeast. In fact northeastern states even have their own name for severe snow storms - nor'easter.

But again, while nor'easters are often associated with large amounts of snow, what truly defines a nor'easter is the wind - this time the direction rather than the speed. Nor'easters are storms that affect the northeastern region of the U.S., traveling in a northeastern direction, with winds coming from the northeast. The Great Blizzard of 1888 is considered one of the worst nor'easters of all time.

Still thing the pending weather is a blizzard? It may be, especially if you live in one of these towns - considered some of the snowiest in the country. Take a look at how the current storm stacks up to some of the worst blizzards in U.S. history.