Friday, June 30, 2006


A blizzard is a severe winter storm condition characterized by low temperatures, strong winds, and heavy snow. They are caused when a high pressure area meets a low pressure area.

Because the factors involving classification of winter storms are complex, there are many different definitions of blizzard. A major consensus is that in order to be classified as a blizzard, as opposed to merely a winter storm, the weather must meet several conditions. The storm must decrease visibility to a quarter of a mile or 400 meters for three consecutive hours, including snow or ice as precipitation, and have wind speeds of at least 35 miles per hour or 56 kilometres per hour (this would be seven or more on the Beaufort Wind Scale).

Another standard, according to Environment Canada, is that the winter storm must have winds of 40 km/h (25 mph) or more, have snow or blowing snow, visibility less than 1 km (about 5⁄8 mile), a wind chill of less than −25 °C (−13 °F), and all of these conditions must last for 4 hours or more, before the storm can be properly called a blizzard.When all of these conditions persist after snow has stopped falling, meteorologists refer to the storm as a ground blizzard.