Places recently hit hard -- like Kerrville, Texas, and Burnet, Texas -- are inside this heightened potential for flash flooding, with any heavy rain and flash flooding that occurs over or adjacent to these areas likely to flow downstream via rivers that run through or nearby these devastated areas.

Two people were killed after their car was swept away by flash flooding in New Jersey. Record-breaking rain in the Northeast was so heavy, flooding spilled over into New York subways and roads, leaving some drivers stranded.

Governor Phil Murphy issued a state of emergency, calling on residents to avoid unnecessary travel and to stay indoors.

Additional dangerous flash flooding incidents are likely in the coming days as high humidity, daytime heat and storm systems interact from the Atlantic Seaboard to the Plains, Gulf coast and Southwest.

Thousands of flash flood warnings have been issued across the country and the number of flash flood emergencies is near-record too.