A flash flood warning was in effect in New York City until 9:45 p.m., and New Jersey Gov. Phil Murphy declared a state of emergency. Middlesex, Morris and Somerset counties remained under a flood warning until 7:15 a.m. Tuesday.

The National Weather Service released a flood warning at 9:51 p.m. on Monday in effect until Tuesday at 1 a.m. for Essex, Passaic and Union counties.

Parts of New York City and Northern New Jersey were inundated on Monday night as widespread thunderstorms moved through.

As the skies opened up over New York City, torrents of rain transformed bustling streets into rivers, leaving residents grappling with an unexpected deluge.

Flooding is causing problems on multiple New York City subway lines as torrential rain pummels the Tri-State Area.

Forecasters say some thunderstorm cells have the potential to dump as much as 2 to 3 inches of rain in one hour, posing a risk of rapid flooding.