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.

White House press secretary Karoline Leavitt later began her briefing on the offensive, calling out those who've questioned whether federal cuts to the NWS impacted staffing levels or forecasting abilities as the tragedy unfolded.

Teams from Missouri, Florida and Mexico are aiding in search-and-rescue efforts as the weather is expected to improve over the next couple days.

Torrential rains before dawn on Friday deluged the Guadalupe River, which burst its banks and killed dozens of people, leaving behind mangled piles of debris, trees and cars.

Rescuers searched the Guadalupe River for survivors of the Texas floods that killed more than 100 people over the July Fourth holiday weekend, with an unknown number of people still missing. The basin area was crowded with families and campers preparing to enjoy the holiday when pounding rain brought about catastrophic flash floods just before dawn Friday.