HOUSTON (AP) — The Houston area was under threat of worsening flood conditions Saturday, a day after heavy storms slammed the region and authorities warned those in low-lying areas to evacuate ahead of an expected “catastrophic” surge of water.

A flood watch remained in effect through Sunday afternoon as forecasters predicted additional rainfall Saturday night, bringing another 1 to 3 inches (2.5 to 7.6 centimeters) of water to the soaked region and the likelihood of major flooding.

Friday’s storms forced numerous high-water rescues, including some from the rooftops of flooded homes. Officials redoubled urgent instructions for residents in low-lying areas to evacuate, warning the worst was still to come.

“This threat is ongoing and it’s going to get worse. It is not your typical river flood,” said Harris County Judge Lina Hidalgo, the top elected official in the nation’s third-largest county.