Mayor Eric Adams has also urged New Yorkers to stay home or seek shelter.
Brooklyn has been particularly hard-hit by rising waters, with alarming videos depicting streets and subways submerged. The MTA, responsible for the city's transit system, reported widespread outages and delays.
A severe storm system has stalled over the city, affecting parts of upstate New York, New Jersey, and Connecticut, prompting widespread flood watches and warnings.
The New York area may experience an unprecedented amount of rainfall, with two to five inches already recorded in some areas since midnight.
Emergency alerts were sent to cellphones in the city at 9:30 am local time by the National Weather Service, warning of a "FLASH FLOOD WARNING" until 12:30 pm EDT, emphasizing the dangerous and life-threatening nature of the situation and advising against unnecessary travel unless fleeing flooding or under an evacuation order.
City authorities issued a travel advisory starting at 4 am on Friday, extending until 6 am on Saturday, with the potential for "widespread travel impacts."