When does a snowstorm become a blizzard? (Meteorologist Q/A at Old Farmer's Almanac)

Question of Day (Jan. 28, 2014) -- posted at www.almanac.com/ -- Please give me the meteorological requirements for a snowstorm to be classified as a blizzard. Answer: A blizzard is a winter storm characterized by high winds, low temperatures, and driving snow for a period of at least three hours. Visibility will often be reduced to less than a mile. According to the official definition given in 1958 by the U.S. Weather Bureau, the winds must be at least 35 miles per hour, and the temperature must be 20 degrees Fahrenheit or lower.