PORTLAND, Ore. (AP) — Wildfires in Oregon are burning an area roughly equivalent to half the state of Rhode Island, affecting air quality throughout the state and forcing the evacuations of more than 4,500 people, fire authorities said Wednesday.

Two dozen fires in southern, eastern and central parts of the state had scorched a total of 571 square miles (1,478 square kilometers).

And although fire crews appreciated cooler weather and some fog on some fire lines, they are bracing for triple-digit temperatures and the return of windy conditions and extremely low humidity later this week and into the weekend, said Terry Krasko, a U.S. Forest Service spokesman.

The largest fire is near the coastal town of Brookings near the California border.

That 196-square-mile (508-square-kilometer) blaze is 5 percent contained and 4,568 people have fled their homes. Firefighters have managed to carve out a containment line along the southwestern edge of the fire to protect the 6,500-person town that will be bolstered by the arrival Wednesday of six Oregon National Guard teams.

The fire started July 12 from a lightning strike in the Rogue River-Siskiyou National Forest but grew rapidly last week.

"That 5 percent doesn't sound like a lot but it's very critical to this town and we feel very good about that. There have been people asking, 'What about the other side of the fire, what about the east?'" Krasko said. "But we have to put our efforts first where the homes and businesses are — where people live. These are our family and friends."

Also in the Rogue River-Siskiyou National Forest, but further east, a complex of fires forced the evacuation of six homes Tuesday in a rural community called Joe Bar near the Applegate River Valley. Several of the fires have merged and firefighters have divided the largest ones into three areas of attack, fire authorities said.

About two dozen blazes all began on Aug. 12 after a lightning storm in the area but most were put out quickly by crews.

In central Oregon, a 34-square-mile (88 square kilometer) fire west of Sisters is now 44 percent contained. No mandatory evacuations are in effect.

Fires statewide continue to generate thick smoke that's affecting air quality in southern and central Oregon.

Smoke forced the Oregon Shakespeare Festival to cancel its outdoor performance on Tuesday.

Nine cities, including Bend, Medford, Ashland and Klamath Falls, had unhealthy air conditions on Wednesday, according to the Oregon Department of Environmental Quality.

Smoke from all the blazes has also converged on Portland, which is several hundred miles away, and has obscured the iconic view of Mount Hood.

On Tuesday, some Portland residents reported finding ash on their parked cars.

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