SAN JUAN, Puerto Rico — Hurricane Erin exploded in strength to a Category 5 storm in the Caribbean on Saturday, rapidly powering up from a tropical storm in a single day, the National Hurricane Center said.

While the compact hurricane’s center wasn’t expected to hit land, it threatened to dump flooding rains as it continued to grow larger.

The first Atlantic hurricane of 2025, Erin ramped up from a tropical storm to a Category 5 hurricane in a mere 24 hours. By late Saturday morning, its maximum sustained winds more than doubled to 160 mph.

The hurricane was located 105 miles north of Anguilla at about 11 a.m. Saturday, moving west at 17 mph. The storm’s center was forecast to remain at sea without hitting landing, passing north of Puerto Rico and the Virgin Islands.

Erin was close enough to affect nearby islands. Tropical storm watches were issued for St. Martin, St. Barts and St. Maarten. The Hurricane Center warned that heavy rain in some areas could trigger flash flooding, landslides and mudslides.

Tropical-storm force wind gusts are possible in the Turks and Caicos Islands and southeast Bahamas.

Though compact in size, with hurricane-force winds extending 30 miles from its center, the Hurricane Center said Erin was expected to double or even triple in size in the coming days. That means the hurricane could create powerful rip currents off parts of the U.S. East Coast later in the week, even with its eye forecast to remain far offshore.

Protruding U.S. coastal areas – such as North Carolina’s Outer Banks, Long Island, New York, and Cape Cod, Massachusetts – face a higher risk of direct and potentially severe tropical storm or hurricane conditions than much of the southern Atlantic, mid-Atlantic and northern New England coasts, AccuWeather said.

Scientists have linked rapid intensification of hurricanes in the Atlantic Ocean to climate change. Global warming is causing the atmosphere to hold more water vapor and is spiking ocean temperatures. The warmer waters give hurricanes fuel to unleash more rain and strengthen more quickly.

Storms that ramp up so quickly complicate forecasting for meteorologists and make it harder for government agencies to plan for emergencies. Hurricane Erick, a Pacific storm that made landfall June 19 in Oaxaca, Mexico, also strengthened rapidly, doubling in intensity in less than a day.

Erin is the fifth named storm of the Atlantic hurricane season, which runs from June 1 to Nov. 30. It’s the first to become a hurricane.

The 2025 hurricane season is expected to be unusually busy. The forecast calls for six to 10 hurricanes, with three to five reaching major status with winds of more than 110 mph.

The U.S. government has deployed more than 200 employees from the Federal Emergency Management Agency and other agencies to Puerto Rico as a precaution as forecasters issued a flood watch for the entire U.S. territory from late Friday into Monday.

Puerto Rico Housing Secretary Ciary Pérez Peña said 367 shelters have been inspected and could be opened if needed.

The U.S. Coast Guard said Friday that it closed six seaports in Puerto Rico and two in the U.S. Virgin Islands to all incoming vessels unless they had received prior authorization.

Meanwhile, officials in the Bahamas said they prepared some public shelters as a precaution as they urged people to track the hurricane.

“These storms are very volatile and can make sudden shifts in movement,” said Aarone Sargent, managing director for the Bahamas’ disaster risk management authority.

Associated Press reporter Isabella O’Malley contributed from Philadelphia.