With tons of water -- and no place for it to go -- rescues from devastating flooding continued in and around Houston overnight.

Flooding is blamed for eight deaths in Texas. A research scientist estimates almost 9 trillion gallons of rain fell on the state over the past three days, and the forecast calls for more rain.

People living in low-lying areas north of Houston evacuated with help from the National Guard -- some families there not taking a chance that things will get worse, reports CBS News correspondent Omar Villafranca.

"What we'll come back to whenever all of this dies down - I'm hoping everything will be okay," said resident Lisa Danna.

In Harris County, streets are still flooded and cars are still underwater. Another exodus is also underway in Montgomery County.

"It's about up to my thigh, inside my house... and it's still coming up," said one resident.

Volunteers worked alongside busy rescue crews and law enforcement to help people who were trapped.

"I do want to send my condolences and on behalf of the city, to the families who did lose loved ones from yesterday," said Houston Mayor Sylvester Turner.

Among those killed was 25-year-old Claudia Melgar. Dash-cam video shows a toll road worker frantically trying to reach her car. She had driven around a barricade and drowned in her SUV before the officer could reach her.

Claudia Melgar. KHOU/Family photo

"She asked her mom if she needed anything, and that was the last we heard from her," said her cousin, Linda Rodriguez said.

Many roads in and around the Houston area are still closed, but Houston schools are back open Wednesday.