Flash flood report
New York City flash flood event report
Modelling the 18 July 2026 NYC metro flash flood, and what advance alerts would have prevented.
Rainfall exceeded NYC's sewer design capacity, and Hurricane Ida.
On 18 July 2026, a flash flood event hit the NYC metro area, with peak rainfall intensity of 3.15 in/hr, well above the area's Hurricane Ida (2021) peak and beyond the city's sewer design capacity. Previsico modelled the resulting flood extent by depth across the metro core in near real time, and calibrated an estimated loss range against Hurricane Ida loss data.
How far the water reached.
NYC metro core, forecasted extent.
NYC metro core, forecasted extent.
NYC metro core, forecasted extent.
NYC metro core, forecasted extent.
$196M to $608M in estimated losses.
This event's peak rainfall intensity of 3.15 in/hr exceeded Hurricane Ida's 2021 Central Park record of 1.75 to 2.04 in/hr. Calibrating against Ida's losses, Previsico estimates the NYC metro area's damage at $196 million under excess-over-capacity scaling (the preferred method), rising to $608 million under a linear intensity scaling upper bound.
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