The 2009 North American Christmas blizzard was a powerful winter storm and severe weather event that affected the Midwestern United States, Great Plains, Southeastern United States, the Eastern Seaboard, and parts of Ontario. The storm began to develop on December 22 before intensifying to produce extreme winds and precipitation by the morning of December 24. The storm's rapid development made it difficult for forecasters to predict. The blizzard was reported to have claimed at least 21 lives, and disrupted air travel during the Christmas travel season. In the Southeastern and Central United States, an outbreak of 28 tornadoes occurred between December 23–24. The storm, a Category 5 "Extreme" one on the Regional Snowfall Index scale, was the first winter weather event to rank as such since the North American blizzard of 1996.

A blizzard is a severe snowstorm characterized by strong sustained winds and low visibility, lasting for a prolonged period of time—typically at least three or four hours. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds. Blizzards can have an immense size and usually stretch to hundreds or thousands of kilometres.