The U.S. National Hurricane Center says Tropical Storm Isaias has strengthened into a hurricane, moving with maximum sustained winds of 130 kph as it churns along the Caribbean.

A hurricane warning is in effect for the Northwestern, Southeastern and Central Bahamas.

Earlier, Tropical Storm Isaias hit Puerto Rico and the Dominican Republic, causing power outages and small landslides.

A tropical storm warning is in effect for the entire southern and northern coastlines of the Dominican Republic, the north coast of Haiti and the Turks and Caicos Islands, according to the hurricane center.

The Associated Press reported late Thursday that Tropical Storm Isaias' powerful winds had hit Puerto Rico, still recovering from other hurricanes and earthquakes, transforming "several streets into fast-flowing rivers and toppled trees and some telephone and electrical cables."

More than 100,000 people are without fresh water.

According to AP, 14 percent of Puerto Rico's cell towers are out.

Emergency workers had to rescue several families who were reluctant to leave their homes for public shelters because of fear of being exposed to the coronavirus at the shelters.

Isaias has blown down trees in the Dominican Republic. Police arrested surfers who refused to heed warnings to find shelter.

The U.S. National Hurricane Center has issued a tropical storm watch for parts of Florida's east coast.

A tropical storm warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A tropical storm watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

U.S. President Donald Trump has signed an emergency declaration for Puerto Rico, which has yet to fully recover from 2017's Hurricane Maria and a recent series of earthquakes.

Isaias is the ninth named storm of a busy Atlantic hurricane season. This is the earliest date a storm beginning with the letter "I" has formed.