Hurricanes are dangerous for several reasons in coastal areas. The high storm winds pile up a mound of water in front of the hurricane, called the storm surge. This mound may be tens of miles in width, and thirty or forty feet in height. When the hurricane reaches a coastline, the storm surge is pushed on the land. This can cause massive flooding of low lying areas. Storm surges are made worse by the high winds of a hurricane, which create large ocean waves, further increasing flooding.

Meteorologists divide hurricanes into five types, based on their wind speed, air pressure, and storm surge. Category 1 hurricanes are the weakest, while Category 5 hurricanes are the worst. Similar scales are used in Asia and Australia to classify typhoons and tropical cyclones.