SPOKANE, Wash. — Smoke from big wildfires burning east of the Cascade Range hurt air quality Wednesday and hampered efforts by crews battling the flames in Washington state.

Smoky conditions grounded helicopters and airplanes that had been fighting the fires, and air quality was rated as unhealthy for some people in Spokane County, which has nearly 500,000 residents.

Crews battling a 262-square-mile blaze near the town of Republic were also battling smoke as well as flames, fire spokesman Donnie Davis said.

“Everybody up here is rubbing their eyes,” Davis said. “It’s brutal.”

Davis said the cause of the fire remained under investigation.

A wildfire in Okanogan — the largest blaze ever recorded in the state — grew to nearly 438 square miles and smoke also grounded air resources, fire spokesman Rick Isaacson said.

“We’re still socked in,” Isaacson said. “There’s maybe 1 mile of visibility.”

The U.S. is in the middle of a severe fire season with about 11,600 square miles scorched so far.

“You can imagine how stretched thin everybody is,” said Dan Dallas, deputy incident commander of the Okanogan fire. “We’re all working without the resources that in a normal year — which I don’t think there is such a thing anymore — that we might have.”

So many fires are burning in Washington state that officials summoned help from fire managers in Australia and New Zealand. They also got 200 U.S. troops from a base in Tacoma in the first such use of active-duty soldiers in nine years.

The Oregon Military Department said soldiers also were ready to help battle a wildfire that has destroyed more than three dozen homes near John Day, about 150 miles east of Portland.

Fires also were burning in California, Montana and Idaho.

Schools reopened near Big Bear (San Bernardino County), where crews were battling a small fire burning through timber near a popular ski resort.

Firefighters have held the blaze to 100 acres.

Residents in Riggins and along U.S. Highway 95 in west-central Idaho have been told to be ready to evacuate. Fire managers said the fire grew to 29 square miles with extreme fire behavior that included sustained runs through tree crowns.

A wildfire that started in the Benchmark area about 30 miles west of Augusta, Mont., led to the evacuation of recreational cabins in the Lewis and Clark National Forest.