The Predator, used in military operations in the Middle East, was deployed by the California Air National Guard following approval by U.S. Defense Secretary Chuck Hagel.
It is being used to monitor conditions on the ground for firefighting personnel.
"The impact of this will be significant," said Air Force Lt. Col. Thomas Keegan, a California National Guard public affairs officer. "It will identify where fire activity is located and how it is moving, as well as where it has been controlled."
The wildfire at the park covers about 160,000 acres. The Predator will monitor the locations of the fire, identify safe routes of retreat for firefighters on the scene and verify new fires created by lightning strikes or floating embers.