The threat of flash flooding on Sunday afternoon was focused over parts of the Midwest, where flood watches have been posted from Missouri to West Virginia, including the cities of Indianapolis and Cincinnati. Rounds of heavy rain and thunderstorms are forecast to sweep across the Midwest region over the next 24 hours.

“If you’ve never seen water rise in front of you in minutes, it’s hard to conceive of how quickly that can happen—and how quickly your life and property can be at risk,” said Rachel Hogan Carr, executive director of the Nurture Nature Center, a nonprofit focused on flood-risk communication.

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.