One helicopter and three ground crews are continuing to battle the blaze, officials with the Department of Natural Resources told KOMO News.
The fire is contained at the lower elevations but growing at the top as it continues to burn its way up the mountain.
A driver on I-90 spotted the blaze just before noon Friday and called it in. By 9 p.m. Friday it had grown to five acres, then doubled to 10 acres overnight.
No evacuations have been ordered and no structures are threatened, but that hasn't calmed the nerves of people who live in the area.
"I just want them to douse it so its all gone," said Cheryl Thompson. "We've been worried about this all summer. Because it's been so hot and dry, we've been worried about this."