A blizzard is a severe weather condition characterized by low temperatures and strong winds (greater than 35 mph) bearing a great amount of snow, either falling or blowing. When these conditions persist after snow has stopped falling, it is called a ground blizzard.
An extreme form of blizzard is a whiteout, where the downdrafts, coupled with snowfall become so severe that it is impossible to distinguish the ground from the air. People caught in a whiteout can quickly become disoriented, losing their sense of up and down as well as their sense of direction. Severe blizzards can also occur in conjunction with arctic cyclones.
The word blizzard is a modern one of unknown origin. It was first widely used after the great American winter storm now known as the "Blizzard of 1880".
This term is also used to describe an activity or situation with similarly chaotic action, such as being 'buried under a blizzard of email' (much as we describe a 'whirlwind of activity').