blizzards have winds of at least 35 mph with blowing or falling snow (photo:NOAA)

What is a blizzard?

There are two somewhat different meanings for the word "blizzard". "Blizzard conditions" technically occur when strong winds (at least 35 mph) combine with either falling snow or snow on the ground to reduce visibilities to 1/4 mile or less for at least three hours. According to this definition, blizzard conditions can occur without any falling snow -- it is just severe blowing snow. This is sometimes referred to as a "ground blizzard", an example of which is captured in this photo (note the blue sky above):
ground blizzard conditions

The other common meaning of "blizzard" is a strong winter cyclone event producing large snowfall accumulations, usually combined with strong winds causing blowing and drifting of snow. The following photo shows an example of this:
blizzard conditions with falling snow and blowing snow

It would be difficult for people agree on the "worst blizzard" ever experienced, since so many factors are involved: how much snow fell, how long the storm lasted, how strong the winds were, how large an area was influenced, whether a major city was involved, how many people died, etc. A couple of the worst blizzards in the U.S occurred in 1888 and 1977. A 1972 blizzard in Iran resulted in approximately 4,000 deaths.
Interesting facts:
STUCK BETWEEN HIGH AND LOW PRESSURE Blizzard winds are created when a strong low pressure area is close to a strong high pressure area. The air "tries" to flow from high pressure to low pressure, but the turning of the Earth causes the air to turn to the right (in the Northern Hemisphere), and the wind ends up flowing around the low pressure area, rather than directly toward it.
(page last updated 11/30/2010)
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