The National Hurricane Center warned that roads in the low-lying barrier islands will become impassable, with waves of 15 to 20 feet crashing ashore.

The National Weather Service has issued coastal flood warnings for the Jersey Shore, while warning of dangerous rip currents along the entire East Coast.

A watch means the ingredients are there for severe weather. A warning means it is happening. But there are differences based on weather type.

Weather hazard maps have nearly 100 colors including six variations of red, a "bisque," "moccasin," cornflower blue, and Dodger blue. Experts are working to simplify the alerts.