PLANTATION, Fla. — Hurricane Irma slammed into the Florida Keys on Sunday morning as a Category 4 storm, uprooting and snapping off trees, filling waterfront streets with surging seawater and knocking out power.

Officials worry that Irma, with sustained winds of 130 mph, will devastate the Keys, a series of low-lying sandbar islands tailing off the southern tip of Florida. The National Weather Service reported the storm’s eye crossed the chain 20 miles from Key West, over the Big Pine, Summerland and Cudjoe Keys.

“Everything is underwater, I mean everything,” said Larry Kahn, an editor for the local newspaper The Keynoter. Kahn has been riding out the storm in a shelter that has no power or supplies.

As early as 8 a.m., sheets of rain were visible down Key West’s legendary Duval Street, with what appeared to be at least several inches of water flowing in the street, videos posted to Twitter showed.

Key West is a popular tourist destination, drawing revelers to the Duval Street bars where pianos duel and frozen drinks flow. Americans make up the bulk of Key West's estimated 2.25 million annual visitors, but the city also attracts Canadians, Germans and the British.

Half of the Keys' economy depends directly on tourism — a $2.7 billion industry — according to county officials.

On the Key West waterfront, several sailboats appeared to have been knocked loose from their moorings and were banging against the concrete dock, according to webcam images and social media.

In the upper Keys, water blocked parts of some northbound lanes of U.S. 1, videos and photos showed. Water levels were 3 feet above normal by 10 a.m., the weather service said. Key West’s highest point is just 18 feet above sea level.

This is the first year on record that the U.S. has been hit by two storms that were Category 4 upon landfall: Harvey and Irma.

Forecasters for days have predicted Key West, at the far southern end of the island chain, would bear the brunt of the storm. The county jail’s 460 inmates were evacuated last week. Tourists were ordered out of the Keys on Wednesday, followed by residents, although many refused to leave as the storm approached.

National Weather Service meteorologist Brandon Fling, who is stationed in Key West, said the pressure was rising and winds were gusting to hurricane force: “All well here at the @NWSKeyWest. #Irma made landfall on Cudjoe Key at 9:10am,” he tweeted.

Once the storm passes, a major concern for officials is access: Reaching Key West requires driving across 42 bridges, some miles long, and each one will have to be inspected before vehicles are allowed back on them, county officials said.

Utilities already parked their service vehicles in multiple locations along the Keys, and authorities said re-opening the airports on Key West and Marathon Key would be a priority.

Key West is home to about 25,000 people, along with a significant homeless population. Of that permanent population, about 5,000 are members of the military, along with their families and support staff.