The National Weather Service began sending flash flood warnings that should have triggered cellphone alerts a little after 1 a.m., while local officials began posting on Facebook about four hours later.

At least 89 people are dead and dozens are still missing after devastating flash floods slammed Texas Hill Country, with water rescues taking place along the Guadalupe River, which rose rapidly early Friday morning to the height of a two-story building.

Parts of the state devastated by flash floods that left at least 82 dead were braced for more heavy rains as forecasters extended flood warnings through Monday evening.