Aug 21, 2021
Showers and thunderstorms streaming northward well ahead of approaching Hurricane Henri resulted in flash flooding across portions of New York City and Western Long Island. This rainfall developed in a moisture-rich environment, with the 8pm sounding from Upton, NY recording precipitable water values around 2.25 inches. Rainfall totals from this predecessor rainfall event ranged from 1-5 inches. The ASOS in Central Park recorded 4.45 inches of rain for August 21, a new record for the date, much
Source: NOAA National Weather Service Storm Events Database (event 981794). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Nassau County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.