Hurricane Irene weakened to a Category 1 hurricane and is bearing down on parts of the Bahamas as it inches away from the Caribbean and proceeds toward the East Coast of the United States.

As of eight p.m. Tuesday, the National Hurricane Center said Irene was about  90 miles East of Great Anigua island, and is moving west-northwest at nine miles per hour, packing 90 miles per hour winds.

Officials believe that Hurricane Irene could pass over northwestern Bahamas by Thursday.

Irene is the first storm to seriously threaten the U.S. in about three years and is expected to hit along the North Carolina coast, heading north into Virginia and up the Chesapeake Bay by Sunday morning.

While Florida is almost out of the danger zone in terms of a direct hit, it's bad news for the Mid-Atlantic States.

We've going to have a very large tropical cyclone move up the Northeastern seaboard in the next five to seven days so just about anybody that lives along the Northeast and Southeast coast of the mid-Atlantic needs to be aware of this and prepare for it,'' hurricane center director Bill Read said during a news conference.

U.S. Federal Emergency Management Agency (FEMA) Administrator Craig Fugate on Tuesday said the entire East Coast should be on alert.

The onset of adverse weather will hit the Carolinas by Saturday, the Miami Herald reported, with treacherous surf conditions starting on Friday.

It is projected to move into the mid-Atlantic states by Sunday and then into the Northeast by Monday, forecasters said.

The impact could be widespread, depending on exactly where the storm goes,'' Read said. We see no reason for it not to be a major hurricane in its track northward up along the gulfstream. We're very concerned about what's going to happen in New England.''

On Monday, Irene eased away from the northwestern Caribbean, leaving nearly one million people in the dark in Puerto Rico, a billionaire's mansion torched by lightning in the British Virgin Islands, and fears of flooding across Hispaniola.

Have a look at the maps below: