Harvey became a Category 3 hurricane Friday afternoon, with sustained winds of 120 miles per hour, the National Hurricane Center said in an advisory.
The National Weather Service issued a warning on Friday saying that parts of Texas "may be uninhabitable" for weeks or months after Hurricane Harvey unleashes what could be the fiercest hurricane to hit the United States in almost a dozen years.
Conditions were deteriorating along the Gulf Coast as Harvey strengthened and slowly moved toward the state, with forecasters warning that evacuations and preparations "should be rushed to completion."
Texas Gov. Greg Abbott warned people that Harvey "is going to be a very major disaster." Abbott said Friday that he's asked President Trump for a federal disaster declaration.
Millions of people were bracing for a prolonged battering from the hurricane. Forecasters labeled Harvey a "life-threatening storm" that posed a "grave risk," saying it could swamp several counties more than 100 miles inland.
Brock Long, director of the Federal Emergency Management Agency(FEMA), says the window for evacuating is quickly closing.
"Texas is about to get hit by a major hurricane," Long said. "We're going to see significant rainfall over the next three days. There's going to be damage."
Landfall was predicted along the central Texas coast, between Port O'Connor and Matagorda Bay. The stretch of coastline spans about 30 miles, roughly 70 miles northeast of Corpus Christi.
The center reports the storm has the potential to produce winds hitting 125 mph and storm surges of 12-feet.
"We're forecasting continuing intensification right up until landfall," National Hurricane Center spokesman Dennis Feltgen said.
Harvey grew quickly Thursday from a tropical depression into a Category 1 hurricane, then a Category 2 hurricane early Friday, before reaching Category 3 status at 2 p.m. CT. The last storm to reach Category 3 hit the U.S. was Hurricane Wilma in October 2005 in Florida.
Superstorm Sandy, which pummeled New York and New Jersey in 2012, never had the high winds and had lost tropical status by the time it struck. But it was devastating without formally being called a major hurricane.
All seven Texas counties on the coast from Corpus Christi to the western end of Galveston Island have ordered mandatory evacuations of tens of thousands of residents from all low-lying areas. Officials in four counties ordered full evacuations and warned there was no guarantee of rescue for people staying behind.