The Dry Gulch Fire in Asotin County is 20% contained and estimated at 46,352 acres, the U.S. Forest Service reported Sunday.
Officials said the fire was started by a lightning strike at 8 a.m. July 7.
The fire is located 15 miles southeast of Pomeroy, Washington, and is being fueled by timber, grass and snags, as conditions are dry in the Pacific Northwest.
The weather has been consistently hot with dry air and light winds, causing concerns, according to forest officials.
Crews fighting the fire have been working to establish control lines, as it has continued to spread to the south and west, moving into rugged terrain.
Multiple resources are being used, including sprinkler systems, to help put out the blaze.