One driver suffered life-threatening injuries in Chattaroy when a tree slammed onto his car, impaling him.
The storms, which arrived Wednesday afternoon, damaged some 40 homes at a Riverside mobile home park that were struck by trees.
The Spokesman-Review reported about 50 residents of the mobile home park were staying at a shelter set up by the Red Cross at Riverside High School late Wednesday.
Marilyn Koenig, who lives at the Riverside Village mobile home park, said the storm reminded her of a tornado as she watched the trees begin to fall.
"I was looking out the window and just saw them snapping," she said. "The wind was just really fierce. It just bent them."
The storms were part of a broader swath of severe weather Wednesday that extended from southeast Washington into the wildfire zones in the central part of the state. Spokane International Airport had a peak gust of 67 mph.
More than 39,000 Avista Utilities customers were without power at the peak of the outages. Another 20,700 Inland Power and Light and 6,500 Kootenai Electric Cooperative customers lost power.
Avista spokeswoman Mary Tyrie said it was too early to say when power would be fully restored.
"This is a significant outage and lots of lines are down," she said.
At the Riverside Village, cars were smashed flat and dozens of mobile homes were damaged - one of which was sliced in half - as dozens of pines snapped or were uprooted in the wind.
Early estimates are that between 35 and 40 mobile homes were damaged among the 200 in the park, said Capt. Megan Hill of Spokane County Fire District 4. No one was injured.
The park is without power and water.
In Chattaroy, a man was impaled by a tree branch after his car was hit by a falling tree as he drove down Big Meadows Road.
"He veered off the road and crashed," Hill said.
The tree branch was sticking out of his abdomen and his right arm was nearly severed, but the man was conscious and talking when rescue crews arrived. He had to be cut out of his car, Hill said.
The National Weather Service reported more than 5,500 lightning strikes in eastern Washington and northern Idaho on Wednesday.