Heavy rains fell quickly in the predawn hours of Friday in the Texas Hill Country, causing the Guadalupe River to rise 26 feet in just 45 minutes.

There was little indication of how torrential the Texas downpours would become before dawn. At least 27 people were killed, many of them children at Camp Mystic.

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.

After a devastating holiday weekend that left dozens dead and many still missing, Central Texas is bracing for more rain. Forecasters warn that additional storms this week could exacerbate already hazardous flood conditions,

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.

The National Weather Service extended a flood watch July 7 through 7 p.m. local time for much of central Texas.

The White House is defending the National Weather Service and accusing some Democrats of playing politics in the wake of devastating floods in Texas.

Some regions in the mid-Atlantic are also facing risks of flooding. On Sunday, Tropical Storm Chantal flooded parts of North Carolina, where more than 10 inches of rain fell near the Chapel Hill area. The Haw River, near Bynum, North Carolina, crested to nearly 22 feet, the highest crest on record there, as a result of those heavy rains.

Texas Hill Country is no stranger to extreme flooding. In the rugged, rolling terrain it’s known for, heavy rains collect quickly in its shallow streams and rivers that can burst into torrents like the deadly flood wave that swept along the Guadalupe River on July 4.

Federal forecasters issued their first flood warning at 1:14 a.m. on July 4. Local officials haven’t shed light on when they saw the warnings or whether they saw them in time to take action.