Multiple rounds of heavy rainfall also moved through the region as a result of favorable precipitable water values, convective instability, and low-level winds.

Additionally, Amtrak, Metro-North Railroad, and NYC Ferry services were delayed or suspended, and airports across the New York City area experienced service disruptions and flight delays and cancellations, including both a terminal being flooded and a ground stop implemented at LaGuardia Airport.

Several attractions, including the Alamo Drafthouse in three locations and the Prospect Park Zoo, were closed as a result of the flooding.

Flooding also occurred across numerous towns and municipalities across New Jersey and Connecticut, causing the Housatonic River to swell in western portions of the latter state.

A weak low-pressure area developed off the East Coast of the United States, absorbing the remnants of Tropical Storm Ophelia on September 29.

[6][7][8] The heavy rainfall occurred after convection developed on the morning of September 29, after the weak low became an upper-level trough, which interacted with a strengthening cold front from the Ohio Valley moving offshore in the Atlantic Ocean.

[12] Favorable precipitable water values, elevated convective instability, and southeasterly low-level winds supported several rounds of heavy rain across the concentrated area.

[12] The mesoscale low-pressure area then moved east on the afternoon of September 29, where the convergence axis and elevated instability again produced heavy rainfall, this time across Long Island, and weak instability values and moisture transport also contributed to rainfall rates of 1–2 inches (25–51 mm) per hour across southern Connecticut and western Massachusetts.

[21] The National Weather Service in New York City issued a considerable flash flood warning for Manhattan, Brooklyn, and Queens as heavy rain fell throughout the region.

[2][53] Outside New York, sewers and roads were overwhelmed by flooding in Hoboken, New Jersey, and mayor Ravinder Bhalla declared a state of emergency.

[61] In Hartford, 4.07 inches (103 mm) of rain fell, which was the highest total across Connecticut and setting a daily rainfall record.

[69][70][71][72] Electrical damage sustained from the heavy rains forced 116 patients to be evacuated and a temporary closure of Woodhull Medical Center.

[73][74] On January 31, 2024, United States president Joe Biden approved a disaster declaration first requested on November 29, 2023, primarily for the New York City area, resulting in financial aid from the Federal Emergency Management Agency to be spent on infrastructure repairs stemming from the floods.