The fire's smoke plume, visible for miles, rose 25,000 feet into the air. The blaze closed 35 miles of U.S. Highway 2, stretching from Leavenworth to Stevens Pass in the Cascade Mountains.
Residents of 860 homes have been told they should leave immediately, fire spokesman Rick Acosta said late Wednesday. A Chelan County emergency management spokeswoman said earlier that another 800 homes were less seriously threatened.
Another fire spokesman earlier estimated the Chiwaukum Creek Fire's size at nearly 2 square miles but Acosta said it was so smoky and the fire had moved so quickly that officials just didn't know how big it was. It was first detected Tuesday.
Nearly 1,000 firefighters were on the lines at the Chiwaukum Creek fire, the Mills Canyon blaze near Entiat and a third wildfire. The containment level on the Mills Canyon fire, the state's largest at 35 square miles, held steady at 40 percent.
Worsening wildfire activity has prompted the governor's offices in both Washington and Oregon to declare states of emergency, a move that allows state officials to call up the National Guard.
State fire assistance was ordered for the Carlton Complex of fires burning in north-central Washington's Methow Valley, where residents of about a dozen homes have been told to leave. Spokesman Jacob McCann said Wednesday evening that complex has burned across 7 square miles with zero containment.
A fire that started Wednesday afternoon in a northeast Oregon field west of Heppner raced quickly across as much as 20,000 acres, or some 30 square miles, before firefighters from two counties got it stopped, the Morrow County sheriff's office said.
Undersheriff Steven Myren said no homes or other structures were lost, "although the fire did get uncomfortably close to some."
Several other fires have blackened parts of Oregon, while blazes encouraged by dry conditions raged elsewhere in the West
In Utah, a wildfire encroaching on homes in the Tooele County town of Stockton had burned about 400 to 500 acres. Utah Division of Forestry, Fire and State Lands spokesman Jason Curry said the fire burned part of a water tower but it's believed no homes have been destroyed.
In central Idaho, the lightning-caused Preacher Fire has scorched nearly 53 square miles in two days, burning quickly through grass and brush. But fire managers said Wednesday they had made good progress.
Evacuation orders have been called off for several rural homes in Northern California as firefighters took advantage of cool, moist conditions.
Some residents near the destructive fire in Shasta County have been advised they may need to evacuate again, and the blaze that has burned more than 10,000 acres or nearly 17 square miles still poses a threat to nearly 70 homes, state fire officials said in a statement Wednesday night.
The fire was 40 percent contained.
Marijuana-growing activity led to the fire breaking out on Friday, authorities said.