Flooding has killed at least nine people, swept away cars, submerged subway lines and grounded flights in New York and New Jersey as the remnants of Hurricane Ida brought torrential rains to the area this week.
New York City Mayor Bill de Blasio described the flooding and weather as a "historic weather event" and the National Weather Service issued a flash flood emergency in New York City for the first time.
Recovery efforts were underway early on Thursday to bring back transportation systems serving millions of residents in the densely populated metropolitan area.
US President Joe Biden pledged robust federal help for the northeastern and Gulf states battered by Hurricane Ida and for Western states beset by wildfires - with the catastrophes serving as deadly reminders that the "climate crisis" has arrived.
"These extreme storms, and the climate crisis, are here," Biden said in a White House speech on Thursday. "We must be better prepared. We need to act."
The president said he will further press Congress to pass his nearly $US1 ($A1.4) trillion infrastructure bill to improve roads, bridges, the electric grid and sewer systems.
The proposal intends to ensure that the vital networks connecting cities and states and the country as a whole can withstand the flooding, whirlwinds and damage caused by increasingly dangerous weather
He visited Louisiana to get a first-hand look at the destruction wrought by Hurricane Ida, the monster storm that devastated the southern portion of the state and left one million people without power.
Biden met Louisiana Governor John Bel Edwards and local officials about the hurricane, which is providing the president with a tough test just after the chaotic withdrawal of US forces from Afghanistan.
The fifth most powerful hurricane to strike the United States came ashore in southern Louisiana on Sunday, knocking out power for more than a million customers and water for another 600,000 people, creating miserable conditions for the afflicted, who were also enduring suffocating heat and humidity.
Hurricane Ida struck the Gulf coast and carved a northern path through the eastern United States, culminating on Wednesday in torrential rains and widespread flooding in New York, New Jersey and surrounding areas. At least nine deaths were reported in Louisiana, with at least another 46 killed in the Northeast.
- Australian Associated Press