Crews search for victims of flooding that has killed almost 90 people in Texas Hill Country, with the risk of more flooding still high in central parts of the state. Authorities said Monday that the death toll was sure to rise.

Historic rainfall fell last week in Central Texas, with the Guadalupe River rising 25 feet in 45 minutes around 4:30 a.m. on Friday, July 4. At least 84 of the confirmed fatalities are in Kerr County, Texas, including at least 27 at Camp Mystic, a summer camp along the river. Last week, Mr. Trump signed a disaster declaration for the region.

ABC News Chief Meteorologist Ginger Zee shares how the fast flood threat developed so quickly and how early people were warned about the dangers.

The Texas summer camp where children died in flooding is in an area meteorologists refer to as "Flash Flood Alley."