Hurricane warnings were in effect for Barbados, St Lucia, Grenada, and St Vincent and the Grenadines.
Beryl's centre is expected to pass about 112 kilometres south of Barbados on Monday morning, said Sabu Best, director of Barbados' meteorological service.
"This is a very serious situation developing for the Windward Islands," warned the National Hurricane Centre in Miami, which said that Beryl was "forecast to bring life-threatening winds and storm surge".
Beryl was located about 570 kilometres east-southeast of Barbados.
It had maximum sustained winds of 215 km/h and was moving west at 33 km/h.
Beryl is expected to remain a hurricane as it heads toward Mexico. (AP PHOTO)
It is a compact storm, with hurricane-force winds extending 30 kilometres from its centre.
Beryl is expected to pass just south of Barbados early Monday and then head into the Caribbean Sea as a major hurricane on a path toward Jamaica.
It is expected to weaken by midweek, but still remain a hurricane as it heads toward Mexico.
Beryl had strengthened into a category three hurricane on Sunday morning, becoming the first major hurricane east of the Lesser Antilles on record for June, according to Philip Klotzbach, Colourado State University hurricane researcher.
It took Beryl only 42 hours to strengthen from a tropical depression to a major hurricane — a feat accomplished only six other times in Atlantic hurricane history, and with September 1 as the earliest date, according to hurricane expert Sam Lillo.
Beryl is now the earliest category four Atlantic hurricane on record, beating Hurricane Dennis, which became a category four storm on July 8, 2005, hurricane specialist and storm surge expert Michael Lowry said.
"Beryl is an extremely dangerous and rare hurricane for this time of year in this area," he said.
"Unusual is an understatement. Beryl is already a historic hurricane and it hasn't struck yet."
Forecasters warned of life-threatening storm surges of up to three metres in areas where Beryl will make landfall, with up to 15 centimetres of rain for Barbados and nearby islands.
Long lines formed at gas stations and grocery stores in Barbados and other islands as people rushed to prepare.
Warm waters were fueling Beryl, with ocean heat content in the deep Atlantic the highest on record for this time of year, according to Brian McNoldy, University of Miami tropical meteorology researcher.
"Please take this very seriously and prepare yourselves," Ralph Gonsalves, the prime minister of St Vincent and the Grenadines said.
Thousands of people were in Barbados for Saturday's Twenty20 World Cup final, cricket's biggest event, with Prime Minister Mia Mottley noting that not all fans were able to leave 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."
Mottley said that all businesses should close by Sunday evening and warned the airport would close by night time.
Meanwhile, St Lucia Prime Minister Philip J. Pierre announced a national shutdown for Sunday evening and said that schools and businesses would remain closed on Monday.
"Preservation and protection of life is a priority," he said.
Caribbean leaders were preparing not only for Beryl, but for a cluster of thunderstorms trailing the hurricane that have a 70 per cent chance of becoming a tropical depression.
"Do not let your guard down," Mottley said.
