The National Weather Service urged people to avoid travel if a flash flood warning was in place for their area.

In Plainfield, New Jersey, two people were killed when their car was swept into Cedar Brook, city officials said. This comes days after two others were killed in severe storms in Plainfield on July 3.

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.

New York and New Jersey hit by torrential rain and flash floods, forcing highway closures, suspending subway lines and flight delays.

The flooding necessitated rescues, grounded planes, and submerged vehicles in waist-high water less than two weeks after flash floods in Texas killed more than 100 people, triggering concerns about the increasing number of flood fatalities in recent years because of heavier rainfall,

Heavy rain swept across parts of the U.S. Northeast on Monday night, inundating sections of New York and New Jersey with flash flooding that stranded vehicles in roadways, closed subway lines.

Heavy rains during the evening brought flooding, road closures and power outages throughout New Jersey, which is under a state of emergency.

The Center Valley area in Upper Saucon Township, where flooding was reported along Route 309, had a recorded 6 inches of rainfall, making it the highest rainfall total in the Lehigh Valley, according to the National Weather Service in Mount Holly, New Jersey. Other areas had about 1 or 2 inches of rain.

New Jersey is under a state of emergency after a flash flood caused at least two deaths in Plainfield and damage across Union County.