The Houston area is bracing for "catastrophic" flooding Friday as severe downpours and extreme weather pummel parts of Texas.
Harris County's Office of Emergency Management moved to its highest activation level Friday morning in anticipation of the imminent flooding, Harris County Judge Lina Hidalgo told reporters during a news conference.
Hidalgo warned residents that the forecast has changed as heavy rains have already fallen in northern Polk County and will make their way to Harris County sooner than expected.
"Right now, you may think if you live in those neighborhoods that things have leveled off and we're good to go, but this threat is ongoing and it's going to get worse," she said. "It is not your typical river flood."
A flood watch is in effect in southeastern Texas and Louisiana. Numerous flash flood warnings are also in effect in Texas.
About 45 miles north of Houston, in Cleveland, Texas, a 12-hour old baby was medevaced by the Coast Guard due "reportedly experiencing low oxygen levels at Texas Emergency Hospital, which does not have a neonatal intensive care unit."
Due to flooding in the area, emergency workers were unable to transport the baby by ambulance.
Hidalgo noted that 700 homes have already flooded in Polk County.
"In some way seeing what's taking place there, it's like seeing the future," Hidalgo said.
The judge estimated that 100 Harris County homes are at risk for flooding.
MORE: 3 lifesaving tactics to use if in a car during a flash floodHarris County issued a disaster declaration Thursday and called for mandatory evacuations for residents living closest to the banks of the East Fork of the San Jacinto River.
Those unable to leave will likely be trapped in their homes for two to three days, she warned.
"If you stay there, not only are you a sitting duck, but you're putting our law enforcement in danger," Hidalgo said.
Hidalgo said first responders have rescued 26 people and 30 pets since Thursday night.
Hidalgo said she has been in touch with Gov. Greg Abbott, who issued a disaster declaration Thursday.
"As flooding conditions and severe weather continue in multiple regions across Texas, I expanded the disaster declaration to add 59 counties to ensure Texans and their communities receive the assistance and support they need to stay safe," the governor said in a statement.
"For Texans in at-risk areas, it is important to remain weather-aware, follow the guidance of state and local officials, and avoid traveling in dangerous flood conditions. The State of Texas continues working with emergency management and local officials to deploy any additional resources needed to provide ongoing support and protect our fellow Texans," he added.
The East Fork of the San Jacinto River was up to 75 feet above sea level Friday afternoon and expected to crest at 78 feet later in the day, according to the forecast. The record is 81 feet set during Hurricane Harvey.
Typically, the river is 45 to 50 feet above sea level, Hidalgo said.
MORE: First heatwave of the year expected to hit Southern states next week"Extreme" river flooding is expected to impact central and east Texas river basins through next week, with "historic" releases by lake and reservoir operators amid the heavy rainfall exacerbating flooding conditions, the governor's office said.
Flooding has caused closures along highways in the region. Abbott's office said state responders aided with "multiple" high-water rescues in central and southeast Texas overnight while urging residents to monitor forecasts and follow guidance from local emergency officials.
Residents are also being impacted by power outages amid the severe weather. More than 2,200 Houston-area customers were without power Friday afternoon, according to CenterPoint Energy's outage tracker.
ABC News' Melissa Griffin contributed to this report.