What determines a blizzard?

According to definitions provided by the American Meteorological Society and the National Weather Service (NWS), a blizzard is a severe weather event that lasts at least three hours. It is characterized by low temperatures, high wind, and reduced visibility due to falling or blowing snow. Specifically the NWS says that wind speeds must be 35mph (or greater) and visibility less then one quarter mile. No official temperature for a blizzard is given, but the definition states that the combination of wind, snow, and poor visibility increases life-threatening conditions when the temperature falls below 20 degrees Fahrenheit.