Hurricane Irene battered the low-lying Bahamas southeast of Florida on Thursday and now churns toward U.S. East Coast -- posing extreme danger to some of the country's largest cities.

The category 3 storm was expected to sweep northward to hit the North Carolina coast on Saturday, before raking the remaining Atlantic seaboard.

New York is the latest of five states to declare a state of emergency in a bid to get ahead of Hurricane Irene that threatens to thrash the U.S. East Coast.

Gov. Andrew M. Cuomo declared emergency on Thursday, following Virginia Gov. Bob McDonnell, New Jersey Gov. Chris Christie, Maryland Gov. Martin O'Malley and North Carolina Gov. Beverly Perdue.

On Thursday, North Carolina, New Jersey, Virginia, and Maryland had already declared states of emergency as the storm approached the East Coast. Mandatory mass evacuations are underway in sensitive coastal areas.

North Carolina was under a hurricane watch late Thursday, and emergency officials were expanding evacuation orders to include more than 200,000 tourists and locals in three coastal communities in the Outer Banks.

Irene will make its closest approach to North Carolina by late Friday night and heavy rainfall is possible as far west as central North Carolina and north-central South Carolina. The storm is likely to remain at Category 2 strength or stronger by Sunday as it moves up the east coast, possibly making a direct hit on New York City, America's largest metropolitan area.

The last big hurricane to hit New York was in 1938, when a Category 3 storm struck Long Island.

But that historic event could be rivaled by Irene, poised to arrive in the northeast by late Sunday at hurricane force, with winds possibly in excess of 100 miles per hour. Major metropolitan areas in New York are facing threats of flooding, downed trees and power lines and major power outages.

The National Hurricane Center said that the storm will likely decrease in strength once it climbs higher up the East Coast through colder water. Still, few storms reach the New York area at hurricane strength.

The following Hurricane Irene tracking from the National Hurricane Center (NHC) will offer an idea of where Irene will be headed in the coming days.

The key thing to watch, though, is the wind speeds; there is a big difference between being hit with a 30 mph wind and a 100 mph wind. The second thing to watch for is probability, i.e. the chances that a wind of certain speed would hit a location.

Three of the NHC maps below are drawn with these two points. Maps 2, 3, and 4 show winds blowing at or above 39 mph, 58 mph, and 74 mph, respectively.

The coloring of Hurricane Irene's path on these maps indicate the probability of such winds hitting the locations, with shades of green representing probabilities 5 to 30 percent, shades of yellow representing 30 to 50 percent, and shades of orange to purple representing 50 to 100 percent.

Map 1 shows the timing of Hurricane Irene, which is expected to hit north Florida by Friday morning, South Carolina by Saturday morning, Virginia by Sunday morning, Maine by Monday morning, and northern Canada by Tuesday morning.