Trump directed federal aid toward the state's recovery efforts in affected areas, the White House said in a statement.
"Assistance can include grants for temporary housing and home repairs, low-cost loans to cover uninsured property losses, and other programs to help individuals and business owners recover from the effects of the disaster," the statement read.
Thomas Bossert, Trump's homeland security adviser, said Friday that Texas Gov. Gregg Abbott requested the disaster declaration earlier Friday.
The declaration allows federal funds to begin to flow to state and local efforts in Texas, and previous presidents have made disaster declarations ahead of major storms.
Trump tweeted his support for FEMA administrator Brock Long on Saturday morning: "You are doing a great job - the world is watching! Be safe."
Later Trump tweeted
that he was "closely monitoring #HurricaneHarvey from Camp David.
"We are leaving nothing to chance. City, State and Federal Govs. working great together!" he added.
Harvey was listed as a Category 4 hurricane
at around 11 p.m. ET Friday, and was downgraded to a Category 1 by Saturday morning. Forecasters said its impact will leave some areas "uninhabitable for weeks or months."
"I would stress that this is a serious storm," Bossert said Friday, urging Texas residents to follow instructions from state and local officials. "This could remain a dangerous storm for several days."
Bossert also sought to allay concerns about the federal government's preparedness to handle a storm as serious as Harvey, given that several key posts related to disaster preparedness are currently filled by interim officials
The Department of Homeland Security has been led by acting Secretary Elaine Duke since retired Gen. John Kelly was tapped to become White House chief of staff. The National Oceanic and Atmospheric Administration's top official is also working in an interim capacity in the absence of a presidential nominee. And the post of deputy FEMA director is vacant as Trump's nominee awaits Senate confirmation.
Bossert touted the qualifications of the President's FEMA director, Brock Long, and said the interim officials overseeing various hurricane relief and response efforts are fully qualified.
"Under that leadership team, we couldn't have a better team, to be honest," Bosser said amid questions about vacancies in Senate-confirmed nominees in several key posts. "Under that DHS team we're in good hands at the federal level."
Trump has been regularly briefed on the storm's progress by Bossert and his chief of staff John Kelly. He has also been in touch with Long and Duke, Bossert said.
Once the storm has passed, Trump may travel to Texas next week, White House press secretary Sarah Huckabee Sanders said.
Bossert offered some details of the President's efforts at the helm of preparations for the federal government's response to the hurricane. He said Trump was primarily concerned about whether Texas residents are "getting out of harm's way;" whether emergency management officials had the "appropriate resources"; and that people in Louisiana, as well as Texas, be prepared in case the storm's path changes.
FEMA and other federal agencies have pre-positioned resources to aid in the relief effort.
Bossert also touted Trump's abilities to lead the federal government as the nation awaited what will be its first Category 3 hurricane to make landfall in almost 12 years.
"This is right up President Trump's alley," Bossert said.
Trump departed Friday afternoon for the presidential retreat at Camp David, where Bossert said Trump would have all necessary resources to continue monitoring the storm.
As Trump boarded Marine One, he offered only a few words to those in Texas bracing for the hurricane: "Good luck to everybody."