New York City Mayor Michael Bloomberg has ordered mandatory evacuations for residents in low-lying coastal areas ahead of Hurricane Irene.
The low-lying areas are scattered across the city and are home to about 270,000 residents. They include parts of Battery Park City, Coney Island and the Rockaways.
Bloomberg calls the mandatory evacuations a first.
Emergency shelters are opening Friday afternoon. Bloomberg says the evacuation deadline is 5 p.m. Saturday.
Officials also ordered an unprecedented shutdown of the city's mass transit system for Saturday.
The Metropolitan Transportation Authority has never before halted its entire system in advance of a storm, though the system was seriously hobbled by an August 2007 rainstorm. The last planned shutdown of the entire transit system was during a 2005 strike.