Hurricane Beryl is forecast to strengthen into a powerful Category 4 storm as it approaches the south-east Caribbean, which began shutting down on Sunday amid urgent pleas from government officials for people to take shelter.

Hurricane warnings are in effect for Barbados, St Lucia, Grenada, and St Vincent and the Grenadines.

“This is a very serious situation developing for the Windward Islands,” warned the National Hurricane Centre in Miami, which said Beryl is “forecast to bring life-threatening winds and storm surge … as an extremely dangerous hurricane”.

Beryl strengthened into a Category 3 hurricane on Sunday morning, becoming the first major hurricane east of the Lesser Antilles on record for June, according to Philip Klotzbach, of Colorado State University.

If Beryl’s winds reach 125mph (201kph), it would be the second earliest such storm in the Atlantic on record, surpassing Audrey in 1957, he said.

Beryl is now only the third Category 3 hurricane ever recorded in the Atlantic in June, following Audrey in 1957 and Alma in 1966, according to hurricane expert Michael Lowry.

Beryl was first located about 465 miles (750km) east-southeast of Barbados. It was a Category 2 storm with maximum sustained winds of 100mph (155kph) and was moving west at 21mph (33kph).

Two hurricane hunters were en route to the storm to gather more details about its intensity, according to the National Hurricane Centre.

Beryl is expected to pass just south of Barbados early on Monday and then head into the Caribbean Sea as a major hurricane on a path towards Jamaica. It is expected to weaken by midweek but still remain a hurricane as it heads towards Mexico.

Forecasters warned of life-threatening storm surge of up to 9f (3m) in areas where Beryl will make landfall, with up to 6in (15cm) of rain for Barbados and nearby islands.

Long queues formed at fuel stations and grocery stores in Barbados and other islands as people rushed to prepare for a storm that has broken records and rapidly intensified from a tropical storm with 35mph (56kph) winds on Friday to a Category 1 hurricane on Saturday.

Warm waters are fuelling Beryl, with ocean heat content in the deep Atlantic the highest on record for this time of year, according to Brian McNoldy, a tropical meteorology researcher from the University of Miami.

“We have to remain vigilant,” Barbadian Prime Minister Mia Mottley said in a public address late on Saturday. “We do not want to put anybody’s life at risk.”

Thousands of people were in Barbados for Saturday’s Twenty20 World Cup final, cricket’s biggest event, with Ms Mottley noting that not all fans were able to leave on Sunday despite many rushing to change their flights.

“Some of them have never gone through a storm before,” she said. “We have plans to take care of them.”

She said all businesses should close by Sunday evening and warned that the airport would close by night-time.

Kemar Saffrey, president of a Barbadian group that aims to end homelessness, said in a video posted on social media on Saturday night that those without homes tend to think they can ride out storms because they have done it before.

“I don’t want that to be the approach that they take,” he said, warning that Beryl is a dangerous storm and urging Barbadians to direct homeless people to a shelter.

Home affairs and information minister Wilfred Abrahams echoed his comments.

“I need Barbadians at this point to be their brother’s keeper,” he said. “Some people are vulnerable.”

Meanwhile, St Lucia Prime Minister Philip J Pierre announced a national shutdown for Sunday evening and said schools and businesses will remain closed on Monday.

“Preservation and protection of life is a priority,” he said.

Caribbean leaders are preparing not only for Beryl, but for a cluster of thunderstorms trailing the hurricane that have a 70% chance of becoming a tropical depression.

“Do not let your guard down,” Ms Mottley said.

Beryl is the second named storm in what is forecast to be an above-average hurricane season, which runs from June 1 to November 30 in the Atlantic.

Earlier this month, Tropical Storm Alberto came ashore in north-eastern Mexico with heavy rain that resulted in four deaths.

The National Oceanic and Atmospheric Administration predicts the 2024 hurricane season is likely to be well above average, with between 17 and 25 named storms. The forecast calls for as many as 13 hurricanes and four major hurricanes.