A flood watch has been extended into Sunday for Houston following catastrophic flooding that turned backyards and streets into rivers and prompted water rescues in nearby communities.

Parts of South Texas, including Harris County, home to Houston, have been hit with heavy rain. Harris County Judge Lina Hidalgo, the county government’s top executive, declared a disaster Thursday as mandatory evacuations were ordered along the East Fork of the San Jacinto River.

Photos posted on social media by Harris County Sheriff Ed Gonzalez showed streets completely covered as first responders brought residents to safety.

“Heroes,” Gonzalez captioned a series of photos of rescuers carrying small children and dogs.

The Harris County Sheriff’s Office rescued 73 people and 42 animals between Tuesday and Saturday morning. More rescues were underway, the office said.

Four million people across the Southern High Plains are at risk for strong to severe thunderstorms Saturday night, including the Texas cities of Austin, Odessa, Lubbock, and Abilene. Hail, a few tornadoes, and damaging wind gusts are all possible.

Hidalgo said in a video posted Friday night that the water along the East Fork of the San Jacinto River almost completely covered mailboxes in some areas and had reached up to the roofs of homes in others.

A flood watch had been in effect for Houston until 7 p.m. Friday but was extended into Sunday afternoon, the National Weather Service in Houston said in a post on X. An additional 1 to 3 inches of rain is possible Saturday night into Sunday.

The agency said isolated thunderstorms should be expected but the main focus will be another round of heavy rainfall.

“Stay weather aware!” the agency wrote. “River flooding continues; stay away from floodwaters!”

Other parts of the country have also been hit with dangerous weather. Rainfall will extend over parts of Oklahoma, Arkansas, and east Texas by Sunday with a lower risk for severe weather. About 18 million in this region are under flood alerts.

In Las Vegas, the National Weather Service issued a High Wind Warning and said possible gusts between 40 to 60 mph are expected.

The weather led to the cancellation of Usher’s Lovers & Friends Festival on Saturday. The festival said in a post on X that ticketholders who used Front Gate Tickets will receive a refund within 30 days.

Usher said he was “disappointed” about the cancellation and “was working on something special to express my heartfelt for each and every one of you who continue to support me.”

On the West Coast, a low-pressure system continues to push onshore, bringing rain, mountain snow, and gusty winds to the region. Wind alerts are in place for 9 million people in the region, including Las Vegas, Reno, Nevada and Santa Barbara, California.

Northern California to Washington will see heavy rain Saturday. Showers will gradually dip south and east towards the Rockies Saturday night and into Sunday.

This article was originally published on NBCNews.com