President Donald Trump has a message for Texans in the path of Hurricane Harvey: "Good luck."

"Good luck to everybody," Trump said on the way to the Marine One helicopter for a weekend trip to the Camp David retreat. "They're going to be safe. Good luck to everybody. Good luck."

Trump, who was holding his granddaughter's hand on the way to the helicopter, pumped his other fist and waved after wishing Texans luck.

Harvey, the first likely natural disaster since Trump took office, is expected to be the biggest hurricane to hit the U.S. mainland in more than a decade. The Category 3 storm is projected to make landfall in southeast Texas late Friday or early Saturday.

Harvey is expected to bring a "life-threatening storm surge" of up to 12 feet and "catastrophic" flooding with up to 35 inches of rain to parts of the Texas coast, according to the National Hurricane Center.

In Louisiana, 10 to 15 inches of rain could fall.

Texas Gov. Greg Abbott has declared a state of disaster in at least 30 counties, and widespread evacuations have been ordered along Texas' Gulf Coast.

The approaching storm marks one of Trump's major domestic problems that does not stem from political strife. The White House has said the president and Federal Emergency Management Agency are coordinating with state and local officials about providing the resources they need.

On Friday, White House press secretary Sarah Huckabee Sanders said in a statement that "the storm will likely be very destructive for several days" and that Trump "encourages people in the path of this dangerous storm to heed the advice and orders of their local and state officials."

"The President's highest priority is the safety of the public and of first responders. Those who ignore evacuation orders could be putting both themselves and first responders in danger," she said.

Trump plans to visit Texas next week.