While the eye (center) of the storm is not expected to make landfall, the hurricane is on course to lash the coast of North Carolina late Thursday before shifting to the north.
Hurricane and tropical storm warnings and watches are in effect along the mid-Atlantic coast and as far north as Maine.
Forecasters from the National Hurricane Center say Earl has begun to weaken, and is now a category three hurricane with maximum sustained winds of 205 kilometers per hour. But they say it is expected to remain a powerful hurricane as it passes near the North Carolina coast.
Forecasters have warned of heavy rains, damaging winds and a dangerous storm surge that could raise water levels along the coast as much as 1.5 meters. The governors of North Carolina, Virginia and Maryland have declared states of emergency.
President Barack Obama also declared a state of emergency in North Carolina, allowing the federal government to coordinate disaster relief efforts there.
Earl already has skirted parts of the eastern Caribbean, flooding parts of Antigua and ripping out trees and blowing down power lines on St. Martin. Officials in the U.S. Virgin Islands and Puerto Rico said they are working to restore electricity to more than 200,000 people.
Forecasters also are watching Tropical Storm Fiona, which is expected to pass near Bermuda early Saturday.
Some information for this report was provided by AP and Reuters.