New York Mayor Michael Bloomberg told residents to be vigilant as Hurricane Irene whirls towards the city, warning that some low-lying and coastal areas might be evacuated.

Speaking to reporters at a Thursday morning press conference in Queens, Bloomberg said the city's Office of Emergency Management was closely monitoring the storm's progress and had activated the emergency operations center. Thursday brought grey skies and intermittently heavy rain to New York, potentially offering a sign of things to come when Irene arrives over the weekend.

The city has already seen the power of Mother Nature once this week, and Mother Nature may not be done with us yet, Bloomberg said.

By the time Irene gets to us, which is forecasted to do sometime on Sunday, it certainly will still be a powerful storm -- possibly as strong as a Category 2 hurricane on Long Island, but anything can happen in terms of its direction and its severity, he added. At this point, the forecast does not indicate that the storm would hit New York City with that strength, but we certainly will still see its effects here, including tropical storm-like conditions such as heavy rains and winds of 60 miles an hour or more.

Bloomberg said that the city might advise people in some neighborhoods to evacuate, although officials plan to wait until Friday night to make the decision. Such an evacuation wouldn't be mandatory, and the mayor said it could effect up to 270,000 New Yorkers. He suggested that people in flood-prone areas seek higher ground as a precaution.

See if that long lost cousin would be willing to put you up overnight,  said Bloomberg.

At risk neighborhoods include Coney Island and Manhattan Beach in Brooklyn, Far Rockaway and Broad Channel in Queens, South Beach, Midland Beach, and other low-lying areas on Staten Island, and Battery Park City in Manhattan.

The Office of Emergency Management has a tool to allow New Yorkers to ascertain whether they live in an evacuation zone. The agency said those areas are especially prone to storm surges, essentially masses of water that hurricane winds can propel onto land.

Storm surge from a strong hurricane would not be limited to waterfront properties and could conceivably push miles inland in some areas, a posting on OEM's Web site said.

New York City's unique geography -- located at a bend in the coastline between New Jersey and Long Island -- makes it especially vulnerable.