CHICO, Calif. — California’s largest wildfire so far this year continued to grow Thursday as it chewed through timber in very hot and dry weather. The Park Fire has scorched more than 660 square miles (1,709 square kilometers) since erupting July 24 near the Sacramento Valley city of Chico and burning northward up the western flank of the Sierra Nevada. Containment remained at 34%, Cal Fire said. The conflagration’s early explosive growth quickly made it California’s fourth-largest wildfire on record before favorable weather reduced its intensity late last week. It reawakened this week due to the heat and very low relative humidity levels. A large portion of the burned area was in mop-up stage but spot fires were a continuing problem, officials said during Thursday morning’s operational briefing. The fire’s northeast corner was the top firefighting priority, operations deputy Jed Gaines said.