The data also highlights critical risks in other areas along the Guadalupe River in Kerr County, revealing more than twice as many Americans live in flood prone areas than FEMA's maps show.

The thunder and lighting came to Camp Mystic first, but that was normal. The storm and the driving rain at the Texas camp woke up some of the campers, including Georgia and Eloise Jones, at about 1 a.m. on July 4. At first the pair thought nothing of it, they told ABC News. After all, it had been raining on and off for days.

Texas records show Camp Mystic had an emergency plan before floods killed at least 27 campers and counselors, but details of its storm response are still unclear.