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.

Flash floods are occurring across the U.S., from Texas to New Jersey. Here's what you should know as risks escalate.

The heavy downpours wreaked havoc across the city with footage showing commuters overwhelmed by floodwaters in various subway stations.

Severe flash flooding struck New York City, Westchester County, Staten Island, and Rockland County, Bergen, Essex, Hudson, Passaic