As it spins offshore, the storm is expected to dump an additional 15 to 25 inches of rain through Friday over the upper Texas coast and into southwestern Louisiana, exacerbating the life-threatening, catastrophic flooding in the Houston area, the hurricane center said.
"As we have done in the past, Mexico stands with Texas in this hard moment", Carlos Gonzalez Gutierrez, the Mexican consul general in Austin, said.
The Army Corps of Engineers says the controlled release into Buffalo Bayou is being done to relieve pressure on the Addicks and Barker reservoirs, which have been overwhelmed by flood waters from Tropical Storm Harvey.
FEMA administrator Brock Long said "FEMA was here before the storm hit, and we will be here as long as needed".
Water overtook the spillway around 8 a.m. local time; at 5 p.m. on Monday, the Corps said the water had reached approximately 105 feet.
"I'm sitting here watching the news and checking the internet and seeing everything going on with Hurricane Harvey and the damage it's causing back home, it's very hard", Watt said in a video he posted to Facebook. The Red Cross said more people were ready to deploy if necessary.
The White House point man on the storm, Homeland Security Adviser Tom Bossert, echoed the president's tweet in a separate interview on This Week Sunday, saying that Trump "doesn't want to get in the way" of relief efforts.
For a glimpse into the scope of Harvey's impact in Texas, the 54 counties included in Abbott's Texas disaster declaration make up 41 percent of the state's 27.9 million population.
To avoid complicating ongoing rescue efforts, Trump will sidestep Houston, where floodwaters are still rising.
The storm is Trump's first major natural disaster in office and will be the first major hurricane to hit the USA since 2005.
But the hurricane will present the Trump administration with challenges even after the storm has passed, with relief efforts and rebuilding expected to stretch years into the future.
"It's going to require the citizens getting involved", he also stated.