The first weather emergency alert sent by the National Weather Service with urgent language instructing people to "seek higher ground now" was sent at 4:03 a.m. local time.

This part of Texas Hill Country is known for flash floods. Why were so many people caught off guard when the river turned violent?

A small Texas town that recorded no deaths in last weekend’s flood disaster had recently upgraded its emergency alert system — the kind of setup state, county and federal officials

Here's what to know about the deadly flooding, the colossal weather system that drove it and ongoing efforts to identify victims.

While the type of flooding we typically see in Houston is vastly different than the flash flooding along the Guadalupe River, the way emergency officials offer warnings is similar.

Flooding is the deadliest natural disaster facing Oklahomans, a threat far greater than tornadoes. In the United States, flooding kills an average of 103 people a year. Tornadoes, however, caused 48 deaths on average during the same period, according to the National Weather Service.