On August 22, Tropical Depression Henri dumped 1.94 inches on Central Park between 10 p.m. and 11 p.m., breaking the record for the most rain in an hour in New York City. Ida bested that record just 11 days later, dropping three inches of rain between 8:51 and 9:51 p.m. on Wednesday night. The intense downpour caused flooding throughout the city, as well as the first flash-flood emergency* ever to be issued in New York City.
– Matt Stieb writing in Intelligencer
*Emergency means the flooding poses an imminent, ongoing severe threat to life, and catastrophic damage.