SAN JUAN, Puerto Rico (AP) — The US National Hurricane Center in Miami said it expected Danny to be near the Leeward Islands by Sunday night or Monday morning, and reach the US Virgin Islands and Puerto Rico early Tuesday.

“The biggest threats to land are the northern Leeward Islands, the Virgin Islands, Puerto Rico and Hispaniola,” said hurricane center specialist Robbie Berg.

Meteorologists said it was too early to predict how much rainfall Danny would generate over Puerto Rico, which has implemented extreme water-rationing measures since May as it struggles with one of the worst droughts in its history.

“This storm has created a lot of expectations,” said Carlos Anselmi with the National Weather Service in San Juan. “But we cannot talk about how much rainfall is expected because the storm is quite small. There’s a lot of uncertainty still.”

Danny had been expected to hit Puerto Rico’s southeast coast, but forecasters said the storm instead was likely to glance the island’s northeast region and drop the heaviest rains over open waters north of the US territory.

The news was disheartening for Puerto Rico residents such as 88-year-old Gloria Rodriguez, who has struggled with water-rationing measures in which hundreds of thousands of people receive water only twice a week.

“We’re asking God to bring us water and not destruction,” she said. “This is what we’re all hoping for.”

Nearly 25 percent of Puerto Rico is considered to be in an extreme drought, and another 45 per cent is under a severe one, according to The National Drought Mitigation Center. A total of 2.9 million people in Puerto Rico have been affected, and US officials have declared at least 20 of the island’s 78 municipalities as disaster zones.

Anselmi said Danny was expected to dump more rain over the US Virgin Islands than Puerto Rico, especially on the islands of St Thomas and St John.

US Virgin Islands Gov Kenneth Mapp said officials were distributing sandbags and had opened shelters as a precaution.

“We do expect tremendous amount of rain,” he said at a press conference Saturday. “We want folks in the community to take this event seriously.”

The approaching storm forced Antigua-based airline LIAT to cancel nearly 40 flights from Sunday to Tuesday, and officials with regional carrier Seaborne Airlines also warned of delays and cancelations. Several cruise ships scheduled to visit the US Virgin Islands have canceled or delayed their trips.

A tropical storm watch was in effect for Antigua, Barbuda, St Kitts, Nevis, Montserrat, Anguilla, St Maarten, Saba, St Eustatius, Guadeloupe, St Barthelemy and St Martin.