Lightning strikes have sparked fast-moving wildfires in Idaho, prompting the evacuation of multiple communities, including one in which a man drove past a building and trees engulfed in flames as a tunnel of smoke rose over the roadway.

Videos posted to social media include a man who said he heard explosions as he fled Juliaetta, about 43km southeast of the University of Idaho's campus in Moscow. The town of just over 600 residents was evacuated just ahead of the Gwen Fire, as were several other communities near the Clearwater river.

The Idaho Department of Lands said “multiple structures” were burned.

As that and other blazes scorch the Pacific Northwest, authorities announced that a wildfire that tripled in size to become California's largest of the year was started by a man who was seen pushing a burning car into a gully. The man then calmly left the area in Bidwell Park, blending in with other people and fleeing the scene as the rapidly spreading flames caused the Park Fire, Butte County prosecutor Mike Ramsey said.