At least 74 high-water rescues occurred overnight in the Houston area, officials said.
The numbers are expected to grow as emergency crews continue to rescue both stranded motorists and people from their homes, Harris County Emergency Management told ABC News.
The National Weather Service office in Houston measured more than 16 inches of rainfall overnight with several more inches expected in the next few hours.
Officials said much of the flooding stemmed from several creeks and bayous that are spilling over their banks.
The Houston school district has closed campuses and offices, citing the floods. Houston metro service has also halted service in the area.