Some 50 million people along the eastern seaboard are likely to be affected by the storm, and the Federal Emergency Management Agency (FEMA) is poised with water, meals and cots and blankets for millions.

For all of their harbor-side advantages, low-lying coastal cities, such as New York, are particularly vulnerable when it comes to major storms, which are predicted to become more powerful with climate change. New York State has initiated long-term plans to build sea walls and discourage waterside development as a means to decrease future high-water threats, but these preparations are still years and decades away. In the meantime, the city is poised to undergo a complete shutdown of mass transit systems and has already evacuated some hospitals and nursing homes. In the event that Irene makes landfall in the city as a category 2 or greater, millions of residents could face flooding on Sunday.

An interactive map of New York City evacuation zones (courtesy of WNYC) shows the areas at risk of flooding in the event of various hurricane categories.

Those battening down the hatches in urban areas face a special set of challenges in preparing for what Obama said is “likely to be an extremely dangerous and costly storm.” Extra supplies can be troublesome to acquire and store, and keeping away from windows in a small apartment can be next to impossible. New York City hurricane preparation guidelines offer some counterintuitive advice for urban dwellers, such as advising those who live in high-rise buildings to take shelter below the 10th floor (if they live in a high-rise and have not been ordered to evacuate altogether).

Numerous Web sites (including Stormpulse and The New York Times) as well as a handful of mobile apps (including Hurricane and iHurricane HD for iPhone users and Hurricane Software for Android) are available to track the storm’s path and intensity—at least as long as internet, cell networks and electricity hold out.