In the early hours of Independence Day, rain pelted sleeping communities in central Texas. No one knew yet how devastating the storm would become.

A swift-moving flood that swept through the Hill Country of Texas on Friday, killing at least 79 people and leaving many more missing, was a flash flood.

As a succession of thunderstorms fed by the remnants of Tropical Storm Barry pummeled Texas' Hill Country, tools used by the National Oceanic and Atmospheric Administration to detect extreme rainfall began “maxing out the color charts.