The remnants of Hurricane Ida triggered spectacular flash flooding and a rare state of emergency in New York City overnight into Thursday, killing at least 14 people in what was called a historic weather event.

Streets turned into rivers while water cascaded down subway platforms, flooding tracks, as transportation authorities effectively shut down services.

"I'm 50 years old and I've never seen that much rain ever," said Metodija Mihajlov whose basement of his Manhattan restaurant was flooded with three inches of water.

"It was like living in the jungle, like tropical rain. Unbelievable. Everything is so strange this year," he told AFP.

Hundreds of flights were cancelled at LaGuardia and JFK airports, as well as at Newark, where video showed a terminal inundated by rainwater.

Flooding closed major roads across multiple boroughs including Manhattan, The Bronx and Queens, with emergency services rescuing hundreds of people.

Ida slammed into the southern state of Louisiana over the weekend, bringing severe flooding and tornadoes as it blazed a trail of destruction north.

New York state governor Kathy Hochul declared an emergency as rain caused massive flooding in the country's financial and cultural capital, leaving the boroughs of Brooklyn and Queens badly hit.

Nine people died in New York City, including eight who could not escape their basements in Queens and Brooklyn, police said. The victims ranged from the ages of 2 to 86.

Another four people lost their lives in Elizabeth, New Jersey, where a state of emergency was also declared, a spokesperson for the mayor there told AFP, while another death was confirmed in Passaic.

Local media reported that at least 22 had died in the New York area.

New Yorkers woke to clear blue skies Thursday as the city edged back to life but signs of the previous night's carnage weren't far away. Residents moved fallen tree branches from roads as subway services slowly resumed.

Around 98,000 homes in Pennsylvania, 60,000 in New Jersey and 40,000 in New York were without power, according to the website poweroutage.us.

"We're enduring an historic weather event tonight with record-breaking rain across the city, brutal flooding and dangerous conditions on our roads," New York Mayor Bill de Blasio said.

The city earlier issued an unprecedented flash flood warning urging residents to move to higher ground.

As footage showed cars submerged on streets across the city, authorities urged residents not to drive on flooded roads.

"You do not know how deep the water is and it is too dangerous," the New York branch of the National Weather Service (NWS) said in a tweet.

The US Open was halted as howling wind and rain blew under the corners of the Louis Armstrong Stadium roof.

The NWS recorded 3.15 inches (80 millimeters) of rain in Central Park in just an hour -- beating a record set just last month during Storm Henri.

It is rare for such storms to strike America's northeastern seaboard and comes as the surface layer of oceans warms due to climate change.

The warming is causing cyclones to become more powerful and carry more water, posing an increasing threat to the world's coastal communities, scientists say.

"Global warming is upon us and it's going to get worse and worse and worse unless we do something about it," said Democratic senator Chuck Schumer.

In Annapolis, 30 miles (50 kilometers) from the US capital, a tornado ripped up trees and toppled electricity poles.

Lingering tornado threat 

The NWS warned the threat of tornadoes would linger, with tornado watches in effect for parts of southern Connecticut, northern New Jersey, and southern New York.

"This is extremely dangerous and potentially deadly flash flooding ongoing in Somerset County, as well as others in the area," the NWS account for the Philadelphia metropolitan area tweeted late Wednesday, along with a video of a car trapped in churning water.

Ida is expected to continue steaming north and bring heavy rainfall on Thursday to New England.

US President Joe Biden is due to travel Friday to Louisiana, where Ida destroyed buildings and left more than a million homes without power.