Tropical Storm Ernesto battered the northeast Caribbean on Tuesday as it took aim at Puerto Rico, where officials closed schools, opened shelters and moved dozens of the US territory’s endangered parrots into hurricane-proof rooms.

Ernesto is expected to become a hurricane early on Wednesday as the centre of the storm moves just north of Puerto Rico on a path towards Bermuda.

Forecasters issued a hurricane watch for the US and British Virgin Islands as well as the tiny Puerto Rican islands of Vieques and Culebra, which are popular with tourists.

“Ernesto could be near or at hurricane strength in about 24 hours,” the US National Hurricane Centre in Miami said in an advisory late on Tuesday morning.

Tropical storm warnings were in place for Puerto Rico, St. Kitts, Nevis, Montserrat, Anguilla, St Martin, St Barts and St Maarten.

The storm is forecast to move over or near the US Virgin Islands on Tuesday evening and pass just northeast and north of Puerto Rico late on Tuesday and early Wednesday.

Heavy rains began pelting Puerto Rico, and strong winds churned the ocean into a milky turquoise as people rushed to finish securing homes and businesses.

“I’m hoping it will go away quickly,” said Jose Rodriguez, 36, as he climbed on the roof of his uncle’s wooden shack in the Afro-Caribbean community of Pinones on Puerto Rico’s north coast to secure the business famous for its fried street food.

Ernesto was about 85 miles (140 kilometres) east of St Croix on Tuesday afternoon.

It had maximum sustained winds of 60 mph (95 kph) and was moving west-northwest at 18 mph (30 kph).

“We are going to have a lot of rain,” Puerto Rico governor Pedro Pierluisi said as he urged people to be indoors by early Tuesday evening.

He activated the National Guard as crews across the island visited flood-prone areas and older residents as part of last-minute preparations.

Meanwhile, Department of Natural Resources officials who work at breeding centres for the island’s only remaining native parrot, the Puerto Rico Amazon, moved them indoors.

Ernesto Rodriguez with the National Weather Service warned that the storm’s trajectory could change as it approaches Puerto Rico.

“We should not lower our guard,” he said.

As intermittent rain pelted Puerto Rico’s northeast, residents in Pinones tried to squeeze in a couple more hours of work.

María Abreu, 25, prepared fried pastries stuffed with shrimp, crab, chicken and even iguana meat as she waited for customers.

“They always come. They buy them in case the power goes out,” she said.

Down the road, Juan Pizarro, 65, picked nearly 100 coconuts from palm trees swaying in the strong breeze. He had already secured his house.

“I’m ready for anything,” he said.

Forecasters have warned of waves of up to 20 feet (six metres) as well as widespread flooding and possible landslides, with six to eight inches (15-20 centimetres) of rain forecast for Puerto Rico and the US Virgin Islands, and up to 10 inches (25 centimetres) in isolated areas.

Puerto Rico has six reservoirs that were already overflowing before the storm.

Officials in Puerto Rico warned of widespread power outages given the crumbling electric grid, which crews are still repairing after Hurricane Maria razed it in September 2017 as a Category 4 storm.

Ernesto is the fifth named storm of this year’s Atlantic hurricane season.

The National Oceanic and Atmospheric Administration has predicted an above-average Atlantic hurricane season this year because of record warm ocean temperatures.

It forecast 17 to 25 named storms, with four to seven major hurricanes of Category 3 or higher.