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.

Radar data can estimate rainfall to a fairly accurate amount. The rain data in the case of the deadly tragedy that unfolded in the Texas Hill Country last weekend shows exactly why the area around Camp Mystic and the Guadalupe River, outside of San Antonio, had such a raging flash flood.