The fire, which began July 14 as four smaller blazes in the Columbia River valley in north-central Washington, was reported to be 16 percent contained Tuesday afternoon. But officials warned that thunderstorms forecast for the area pose a new danger -- mudslides and flash floods -- as heavy rain hits hillsides stripped of vegetation.
There were seven major wildfires in the state Wednesday. But the Carlton Complex, one of the largest in Washington history at 250,000 acres, was responsible for about 75 percent of the land area burned.
More than 2,000 firefighters are trying to contain the blaze.
Inslee discussed the fire with President Obama when the two men met at a Seattle fundraiser Tuesday evening. The president signed an emergency declaration Wednesday allowing federal agencies to coordinate the response to the fire and to provide equipment.
"It's still a growing and dangerous beast, and we have a long, long ways to go in the fire season -- months -- before we're out of the woods," Inslee said.
The fire has destroyed about 200 homes and has been blamed for the death of a man who had a heart attack while trying to protect his property. Okanogan County is without electrical power because lines and poles have burned, and officials say restoring the distribution system could take weeks.
The National Weather Service, which forecast thunderstorms and heavy rain in the region, warned that unstable hillsides can collapse in 10 minutes.
"Water can be as bad as fire if you're in the wrong place," Inslee said.
A prolonged drought has left grasslands and forests in California, Oregon and Washington burned dry. Fire agencies have been dealing with the kind of fires that might normally be expected in the late summer and fall.