Heavy rains and top sustained winds of 85 kilometers per hour are lashing the Windward Islands on Tuesday as Tropical Storm Dorian moves into the Caribbean Sea.
The U.S. National Hurricane Center said the storm could drop between seven and 20 centimeters of rain on St. Lucia, Martinique and St. Vincent.
Dorian is also bringing with it the threat of dangerous surf.
The government of St. Lucia warned people that flooding and landslides were likely. It said people should avoid coastal areas and small boats should stay in port.
Forecasters expect Dorian to gain some strength on Tuesday and to reach hurricane status by the time it moves near Puerto Rico, Haiti and the Dominican Republic on Wednesday.
U.S. President Donald Trump took note of the advance of the storm on Puerto Rico, a U.S. territory devastated by Hurricane Maria in 2017, leaving the island in shambles and believed to have killed nearly 3,000 people.
"Wow! Yet another big storm heading to Puerto Rico. Will it ever end? Congress approved 92 Billion Dollars for Puerto Rico last year, an all time record of its kind for 'anywhere,'" Trump said on Twitter.
Trump, however, way overstated the aid to Puerto Rico; it's actually about $14 billion, and more hurricane relief assistance was sent to the southern states of Florida and Louisiana after the disastrous Hurricane Katrina in 2005.
Forecasters believe Dorian could threaten the U.S. mainland in Florida by the weekend as a minimal hurricane, packing winds of at least 112 kilometers per hour.