More than 65,000 people have fled their homes in the US state of Washington as multiple wildfires continue to ravage the landscape, obliterating hundreds of structures.

"As many as 65,000 people have had to evacuate,” the American Red Cross confirmed on Monday.

The organisation noted that preliminary assessments indicate the flames have already consumed more than 700 homes, primarily within Spokane County.

Spokane County Sheriff John Nowels told a news conference that authorities apprehended a man on a first-degree arson charge.

The suspect is allegedly linked to the Old Trails Fire, one of several blazes currently threatening the area.

The Spokane Complex Fire Incident Management Team reported that more favourable weather is allowing crews to make progress on the fire lines.

Data from the interagency system InciWeb showed that the fires near Spokane and Stevens counties have scorched 8,026 acres (3,248 hectares) since starting on Saturday.

These fires currently remain at 0 percent containment. Other parts of the state face even larger threats.

The Sinlahekin fire has grown to 85,000 acres (34,398 hectares) since it was triggered by lightning on July 26.

More than 820 personnel are battling that blaze, which also has no containment.

Meanwhile, the Little Giant Fire northwest of Leavenworth has burned 51,298 acres (20,759 hectares) in the Okanogan-Wenatchee National Forest.