Tropical storm Fiona is gaining strength as it heads toward Puerto Rico, prompting alerts for "life threatening floods and mudslides" for the US territory and watches for the US Virgin Islands.
One man was found dead in the French Caribbean island of Guadeloupe, after heavy rains from the massive storm swept away his house in the Basse-Terre district, according to local authorities.
On Saturday, the storm was about 120 kilometres southeast of St Croix and about 240km southeast of Puerto Rico with maximum sustained winds of 95km/h, according to National Hurricane Center (NHC).
It was expected to become a hurricane on Sunday and into Sunday night, as it moves near Puerto Rico. A storm is considered a Category 1 hurricane when sustained wind speeds reach 120km/h or greater.
The island was braced for up to 40cm of rain and high winds that could bring flooding, mudslides and power outages.
Heavy rains from Fiona were also due to spread to the Dominican Republican on Sunday and to the Turks and Caicos Islands on Monday night.
The government of the Dominican Republic issued a hurricane warning for the east of the country, from Cabo Caucedo to Cabo Frances Viejo, NHC said.
On Saturday, residents in Puerto Rico were bracing for severe power outages as the island's grid remained fragile after Hurricane Maria in September 2017 caused the largest blackout in US history. In that category 5 storm, 1.5 million customers lost electricity with 80 per cent of power lines knocked out.
Authorities have opened about 80 shelters and closed beaches and casinos, and residents were urged to seek shelter.