Crews battled six large fires in Central and Eastern Washington on Friday and Saturday amid concerns about hot and dry conditions that have prompted burn bans across the rest of the state.

The Mills Canyon fire, southwest of Entiat, grew by about 2 square miles to 34 square miles of grass and brush near Entiat, roughly midway between Seattle and Spokane.

More than 760 firefighters worked to contain the blaze Saturday. The fire threatened 231 structures, with residents of 109 structures under an evacuation order, according to the Northwest Interagency Coordination Center.

Hotshot crews from Washington and Oregon have continued work on the uncontained perimeter of the fire. On Saturday they were working to protect 14 homes along Roaring Creek, near the fire’s northern edge. Another priority was digging fire lines along the southwestern edge to contain the blaze.

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The Lake Spokane fire had burned more than one and a half square miles by Friday and was 30 percent contained. Residents at 60 homes were told to be prepared to leave at a moment’s notice.

Six to 10 households were told to evacuate the area threatened by the 25 Mile Creek fire about 25 miles south of Lake Chelan. The fire, which was reported Thursday, remained at 400 acres Friday evening and was completely uncontained.

The Rock Hill fire, about 13 miles west of Mansfield in Douglas County, was fully contained by Friday. The fire burned three square miles, destroyed two homes and damaged six other structures.

The causes of the fires are unknown, according to the Northwest Interagency Coordination Center.

State officials have extended an outdoor burn ban to include all 13 million acres of lands that the state protects because they’re worried hot, dry weather could increase fire danger

A heat wave throughout the state is projected to last into next week, increasing the potential for wildfire on both sides of the Cascades, according to the Department of Natural Resources. The National Weather Service has issued a heat advisory for most of the Puget Sound area from 11 a.m. Saturday to 6 a.m. Monday, with temperatures expected to reach 90 degrees every day through Tuesday, meteorologist Dana Felton said.

The longest streak of 90-plus degrees in the city is five days, set in 1941 and matched in 1981. Felton said it’s possible this heat wave could break that record, especially since rain isn’t forecast for at least seven more days. The temperatures are well above average; the normal high for this time of year is 75 degrees, Felton said.

“We’re definitely locked into summertime,” he said.

Temperatures will climb even higher east of the Cascades, with some places reaching 104 degrees this weekend and little relief from the heat overnight, according to the Weather Service.

Paige Cornwell: 206-464-2530 or Information from the Associated Press was included in this report.