Tens of millions of people along the US East Coast braced themselves yesterday for Hurricane Sandy, a gigantic storm forecast to assault the densely populated region with battering winds, dangerous flooding and even heavy snowfall.

Sandy could deliver a harsh blow to major cities in its target zone including New York, Philadelphia, Washington, Baltimore and Boston. Its centre is forecast to strike New York-New Jersey area and then move inland toward Philadelphia and the rest of Pennsylvania.

The sheer size of the storm means its effects would be felt from the mid-Atlantic states to New England. Officials warned of widespread power outages that could last for days.

In New York City, subway, bus and train service have been suspended and up to 375,000 people were ordered to evacuate from low-lying areas.

President Barack Obama, speaking after a briefing at the federal government’s storm response centre in Washington, called Sandy a “serious and big storm” and asked residents to heed the orders of state and local authorities to protect themselves from its onslaught.

“It’s a very, very large system,” National Hurricane Centre Director Rick Knabb said. “The storm is going to carve a pretty large swath of bad weather, both water and wind.”

Worried residents in the hurricane’s path packed stores, searching for generators, flashlights, batteries, food and other supplies in anticipation of power outages.

New York City schools are shutting. Other local governments also announced school closures.

Gale-force winds were already starting to buffet Virginia and could reach other parts of the mid-Atlantic coast. Tens of millions of people will feel its bluster for as long as two days, Knabb said.

Forecasters said Sandy was a rare, hybrid “super storm” created by an Arctic jet stream wrapping itself around a tropical storm, possibly causing up to 30 centimetres of rain in some areas, as well as up to 60 centimetres of snowfall in the Appalachian Mountains from West Virginia to Kentucky. It could be the largest storm to hit the US, according to the National Oceanic and Atmospheric Administration’s (NOAA) website.

Sandy was already disrupting transportation systems. More than 700 flights, including international ones, were cancelled yesterday and nearly 2,500 more have been cancelled for today, FlightAware.com said.

New Jersey casinos were ordered to close and state officials decided to shut bus and rail systems by early today.

Governors in other states put National Guard troops on alert. “We’re just asking people to be patient and be ready for a long haul. But we have a very aggressive power restoration programme in place and I think we’re ready,” Virginia Governor Robert McDonnell told the CNN programme “State of the Union.”

In Washington, Obama said officials had assured him that they had all the resources they needed in place. “We’re going to cut through red tape and we’re not going to get bogged down in a lot of rules,” said Obama, who was having to juggle both his re-election bid and his efforts to stay on top of the storm’s impact just nine days before Election Day. Sandy blew the presidential race off course, forcing Obama and Republican challenger Mitt Romney to cancel scheduled campaign stops. It fueled fears that the storm could disrupt early voting ahead of the November 6 election.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.