Hurricane Beryl was barreling west toward Jamaica as a Category 5 storm early Tuesday morning, hours after it carved a trail of destruction across the southeast Caribbean and killed at least two people, officials said.

Beryl strengthened into a Category 5 storm late Monday, meaning it had maximum sustained winds of at least 157 miles per hour, according to the National Hurricane Center of the United States. It was forecast to bring hurricane conditions to Jamaica on Wednesday.

Major Atlantic hurricanes have maximum sustained winds of 111 m.p.h. or higher on a five-tier scale that was developed in the 1970s. By Tuesday morning, Beryl had sustained winds near 165 m.p.h., the National Hurricane Center said. No Atlantic storm has ever grown to Category 5 strength this early in the season, according to Philip Klotzbach, a Colorado State University meteorologist who specializes in tropical cyclones.

Beryl roared across several Caribbean islands on Monday, and two deaths were later reported in Grenada and St. Vincent and the Grenadines.

The storm made landfall on Carriacou, a small island north of Grenada, on Monday morning and “flattened” the island in just half an hour, Prime Minister Dickon Mitchell of Grenada said in a briefing broadcast on social media. Government officials also expected “extreme” damage on the neighboring island of Petite Martinique.

One death was reported in Grenada’s capital, St. George’s, after a tree fell on a house. “This hits home,” Mr. Mitchell said. “The deceased person is in fact the relative of one of the persons who spent the last 36 hours with us here at the National Emergency Operating Center.”

Just north of Carriacou, several islands in St. Vincent and the Grenadines also suffered “immense destruction,” Prime Minister Ralph Gonsalves said in a social media briefing. One death was reported, and hundreds of homes, schools and churches were severely damaged, he said.

An estimated 90 percent of houses on Union Island had been severely damaged or destroyed, and similar levels of destruction were expected on the islands of Mayreau and Canouan, Mr. Gonsalves said.

Beryl, the first Atlantic hurricane of the season, left a trail of destruction in its path as it made landfall: trees snapped in half, extensive storm surge and roofs blown off as winds reached more than 150 miles per hour.

In Grenada, the complete scale of the damage on Carriacou and Petite Martinique would not be clear until Tuesday morning, Mr. Mitchell, the prime minister, said, adding that he would travel to Carriacou as soon as it was safe to do so. There was no power on Carriacou and Petite Martinique, and communication was difficult, officials said.

Early reports of damage also emerged in the capital as the storm passed over the main island. The roof of a police station was ripped away and a hospital had to evacuate patients to a lower level after its roof sustained damage.

Beryl was an anomaly in what is already an unusually busy storm season, which extends until the end of November. When it developed into a Category 4 storm on Sunday, it was the third major hurricane ever in the Atlantic Ocean in June — and the first time a Category 4 materialized this early there in the season.

The storm was also historic for the short time it took to strengthen from a tropical depression to a major hurricane — 42 hours — a direct result of the above-average sea surface temperatures. The quick escalation was a feat recorded only six other times in Atlantic hurricane history.

Officials in Barbados said on Monday that the island had been spared the worst of Beryl.

The prime minister of Barbados, Mia Mottley, told a nationwide broadcast from the island’s emergency operations center that as many as 20 fishing boats, including two popular cruisers, had possibly sunk. Still, she added, “This could have been far worse for us.”

Roughly 40 homes were known to have sustained roof or structural damage so far, Ms. Mottley said, though that number was expected to rise as more than 400 residents returned home from shelters.

People across the eastern Caribbean had started preparing for the storm over the weekend, including those doing some last-minute shopping for supplies.

“Hurricanes are not something that we take lightly at home as a family,” said Fleur Mathurin, who lives on St. Lucia, where some parts of the island were experiencing power outages. “Having my family, my grandmothers, great-grands, gone through Hurricane Allen and Gilbert, this is something that they always preach to us.”