Five people died as a result of the storm in North Carolina, and three were killed in Virginia due to falling trees, emergency officials said, according to CNN.
In the Washington area, roughly 500,000 homes and businesses were without power. Thousands of flights were cancelled, the Bay Bridge was closed and flooding was expected.
"Our No. 1 message for individuals and families up and down the eastern seaboard this morning is that we're not out of the woods yet," said Homeland Security Secretary Janet Napolitano at a news conference on Sunday. "Irene remains a large and potentially dangerous storm. Hazards still persist in communities that have already seen the storm pass."
"Our local, state and federal partners in North Carolina, Virginia and other mid-Atlantic states remain focused on search and rescue, debris removal from critical roadways and other critical missions this morning," Napolitano added.
President Obama, who cut short his Martha's Vineyard summer vacation to bring his family home to the White House, has received regular briefings on the storm from federal emergency officials.
Obama visited FEMA headquarters in Washington on Saturday. "It's going to be a long 72 hours," Obama said in what has become a daily video conference with preparedness officials and others, including representatives of big-box stores signed on for emergency relief efforts.
"This is obviously going to be a touch and go," he told FEMA employees.
FEMA directed people in the hurricane's path to websites, Twitter feeds, Facebook pages, and mobile apps.
Nongovernmental organizations and companies got in on the action as well. Google and Facebook both have web pages dedicated to information about the storm.
Obama declared disasters in Maryland, New Hampshire, New Jersey, Connecticut, Rhode Island, Massachusetts, New Jersey, Virginia, and New York to free up federal aid before any flooding or wind damage to and help in preparations.
DHS deployed three Disaster Medical Assistance Teams to staging areas, with doctors, nurses, paramedics, and pharmacists trained to provide emergency health and medical support.
FEMA Incident Management Assistance Teams were staged in South Carolina, North Carolina, Virginia, New York, Massachusetts, Vermont, D.C., Connecticut, Delaware, and Rhode Island.
Defense Secretary Leon Panetta issued a prepare-to-deploy order for 6,500 active duty troops, who would deploy in support of hurricane relief efforts if ordered, according to Pentagon spokesman George Little.
Little said that it has taken Panetta only 5 to 7 minutes on average to approve requests from states for Defense Department support.
McGovern said her organization was anticipating the storm would affect a "huge geographical area" and that it could take "weeks, maybe even months" to fully respond to damage and needs.
She said the Red Cross was ready to serve 250,000 meals a day, which could be increased to 1 million, and has 15,000 shelters in the affected area.