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.

Waters rushed into subway stations, making for hellish commutes, and the flash floods killed two people in New Jersey and caused a house to explode in New Jersey. Climate experts expect flooding to worsen and threaten already-struggling infrastructure throughout the region.

Forecasters warned more rain and flash flood risk is expected on July 15 after storms flooded out roads the day before.

When the train doors opened, "quite a lot of water came in, so almost all of us stood up on the seats," a passenger told Newsweek.

The subway system, which is more than a century old, is relied on by millions of passengers every day and weaves the city into a cohesive network.

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

Roads and streets, meanwhile, are likely to flood during the downpour, said the Office of Emergency Management’s advisory. Flooded roads could spell trouble for the city’s bus riders and drivers. The city warned motorists not to drive through flooded roads.

Severe storms brought flooding to New Jersey and Pennsylvania, resulting in two deaths, a house fire, and over 100 flight cancelations at Newark Airport.