Federal Emergency Management Agency Administrator Craig Fugate said the main concern is possible flooding.

"The primary threat here is going to be storm surge. We use tropical force winds, however, as a benchmark to have an evacuation completed because many of the overland routes will include high bridges and other things that tropical force winds make it extremely dangerous," said Fugate.

Earlier, heavy rains from Earl caused flooding in low-lying areas of Antigua, and winds ripped out trees and blew down power lines on the nearby island of 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 who were affected by the storm.

Meanwhile, forecasters said residents of the eastern Caribbean should prepare for possible impact from another storm that has formed in the Atlantic. Tropical Storm Fiona is expected to reach parts of the area by Wednesday.

Bill Reed of the National Hurricane Center says Fiona is not expected to come as close to land as Earl did.

"It is forecast to remain northeast of the islands and not impact the U.S. Virgin Islands and Puerto Rico in the same places that were hit by Earl. It is running parallel to Earl and off to the east, maybe impacting Bermuda by the weekend," said Reed.

Current forecasts show Fiona moving north on a path that will keep it far off the U.S. East Coast.