Residents of several Caribbean islands are bracing themselves for the arrival of a strong hurricane over the next 24 to 36 hours.
Hurricane Frances lashed the Florida coastline
Hurricane Ivan is moving towards Barbados, St Vincent, St Lucia, Trinidad and Tobago, Grenada and Martinique, US officials said.
The warnings came as Hurricane Frances threatened Florida once again.
The storm was blamed for at least three deaths and the loss of power for six million people when it hit on Sunday.
It returned, into the Florida Panhandle in the north of the state, on Monday. Forecasters warned it could bring up to 10 inches (25cm) of rain.
By 1500 GMT on Monday, Hurricane Ivan was 435 miles
(700km) east-southeast of Barbados, the US National Hurricane Center said.
It was racing towards the islands at almost 23 mph (35 km/h).
A hurricane warning was issued for Barbados, St Vincent and the Grenadines, St Lucia and Grenada.
Martinique was put on hurricane watch, while a tropical storm warning was issued for Trinidad and Tobago.
Forecasters expected that the storm, the ninth tropical cyclone and fourth hurricane of the current storm season, would make landfall late on Tuesday.
Many people in the Windward Islands live in simple homes, with old wooden structures in areas prone to flooding.
In Barbados, emergency services director Judy Thomas made a televised plea to residents not to be complacent about the storm.
She urged Barbadians to store water, emergency power supplies, dry foods and key medicines.
Almost three million people in Florida left their homes to avoid Hurricane Frances, which lashed the Bahamas last week.
As the storm headed north on Monday evening, residents in southern Florida began returning to their homes.
The Associated Press reported traffic tailbacks of up to five miles as motorists queued for petrol, and long lines for people wanting to stock up water, ice and other basic supplies.