What’s a nor’easter?

Waves crash over Winthrop Shore Drive, Mass. as Hurricane Sandy comes up the coast, Oct. 2012. After inflicting a lot of damage, Sandy became a nor'easter and dampened efforts to restore power and aid victims. See more Hurricane Sandy pictures.
Darren McCollester/Getty Images

Don't like the weather? If you're in the U.S., simply migrate a state or two away and you'll find yourself in an entirely different weather system. The West Coast has torrential rains. The Midwest has blizzards. And the Southern Plains have tornadoes. But the East Coast sometimes receives all three -- in the form a nor'easter.

A nor'easter is a type of massive cyclonic storm that forms within 100 miles (160 kilometers) of the United States' East Coast, traveling inland into the New England and Mid-Atlantic regions and reaching northward to the Atlantic-facing side of Canada. Also called "northeasters," these storms take their name from the strong and continuous northeasterly winds that blow them ashore.

Although nor'easters can occur any time of year, they are most frequent from September to April. In the winter months, a nor'easter can be especially dangerous. It draws cold air from the Arctic air mass, which then collides with warm air from the oceanic Gulf Stream that acts as fuel for the nor'easter. This difference in temperatures turns a nor'easter from an inconvenience into a dangerous storm that introduces frigid temperatures, coastal flooding, hurricane-force winds, blizzard conditions and occasional tornadoes into one of the nation's most populated areas [source: NOAA].

The Mid-Atlantic and New England regions are crowded with cities -- Washington, D.C., Baltimore, Philadelphia, New York and Boston -- known for their influence, whether by resident populations, Wall Street transactions or political machinations. Nor'easters can affect these cities' inner workings; for example, causing Wall Street to shutter in October 2012 for only the second time in a century [source: Schaefer].

The Mid-Atlantic and New England areas also are home to 180 counties that line the East Coast, and during a nor'easter, they become prime targets for beach erosion, flood and property damage [source: NOAA].