A flash flood emergency remains in effect for Harris County, meaning life-threatening flooding is possible.
There are reports of flooded homes all over the Greater Houston Area.
Desperate flood victims trapped in their homes are taking to Twitter to plead for help.
Five people have died in the Houston area in unconfirmed flood-related deaths, according to the National Weather Service.
"This is of epic proportions. I've never seen anything like it," Houston Police Chief Art Acevedo said early Sunday.
The hardest hit areas appear to be south of I-45.
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There is "extraordinarily dangerous flooding" in southeast Houston, according to Jeff Lindner with the Harris County Flood Control District.
"We are getting calls from people climbing into their attic. This is along I-45 between downtown and Clear Lake," Lindner said. "This is along Berry Bayou, Beamer Ditch, Turkey Creek, portions of Clear Creek, Vince Bayou, Little Vince Bayou in Pasadena," he said.
They've had 15 to 30 inches of rain in six hours.
In west Houston, a woman drowned after getting stranded in floodwaters, according to County Judge Ed Emmett. The woman tried to get out of her car on Warrenton near Gessner but she didn't make it. A neighbor found her body about 30 yards from her car.
Several major roadways remain underwater so everyone should stay off the roads.
First responders, risking their lives to save others, are having a tough time keeping up with the calls. There have been more than 500 rescues, Chief Acevedo said.
Emergency officials in Houston are urging everyone not to call 911 unless your life is in danger.
Several bayous are out of their banks or close to it.
A Flash Flood Warning is in effect for Grimes, Harris, Liberty, Montgomery and Waller County until 7:15 p.m.
Before the flooding rain started Saturday evening, tornados caused damage in Cypress, Sienna Plantation, Katy, Richmond and Atascocita. There were no reports of injuries.
As for the immediate forecast for Houston, we have a 100 percent chance of rain through Tuesday. Houston could receive 15 to 20 inches of rain before this is over.