Damaged power lines burn in Nag's Head on August 27, 2011. But it’s not just wind that East Coast residents should be worried about. (NICHOLAS KAMM/AFP/GETTY IMAGES)

The term, not very well known outside hurricane-prone areas, is a rise in water that goes over the predicted tide because of a storm. The NOAA explains: “Along the coast, storm surge is often the greatest threat to life and property from a hurricane. In the past, large death tolls have resulted from the rise of the ocean associated with many of the major hurricanes that have made landfall.”

This is the reason that residents of low-lying areas on the East Coast have been told to leave their homes.

Storm surge is a major worry for residents of New York City. Luckily Irene’s “dirty side,” or its more powerful eastern side, will most likely miss New York, Our Amazing Plant reports, preventing the major catastrophe some had predicted. Still, Mayor Michael Bloomberg once again told people in low-lying areas that they must leave their homes. Consolidated Edison Co. may turn off power in these low-lying areas as a preemptive measure.

In Nags Head, N.C., New York Times reporter Brian Stelter reports that the water in the Albemarle sound has drained from the small island, causing flooding on the other side of the sound. It’s considered a “reverse surge.” When the water returns it risks overflowing into Nags Head.

Check out this map from the NOAA that predicts the storm surge based on the Category of hurricane.