The blaze also burned an outbuilding near the historic St. Mary's Mission while nearing the Paschal Sherman Indian School, said Kathy Moses, public information officer for the Mount Tolman Fire Center.
The school has about 300 students. About 30 boarding students were evacuated to a motel in Omak and classes were canceled Wednesday.
The fire broke out Tuesday along a highway and spread through grass and sagebrush to about 1,000 acres in winds up to 35 mph, Moses said. The cause was under investigation. No injuries were reported.
Flames jumped a highway overnight and burned four or five outbuildings in addition to the residences.
"When you lose two homes, it is alarming," Moses said.
Some other residents near the fire were told they may need to evacuate, she said.
A state management team is taking over the firefighting and bringing more crews to help about 100 firefighters from the Colville Confederated Tribes, Omak and Okanogan County.
Washington has received little rain in the past two months. A Sept. 8 lightning storm started dozens of fires in Eastern Washington and five major fires burned a total of 186 square miles. Officials said the embers will smolder until significant rain or snow falls.