Crews battling the largest wildfire in California this year braced for thunderstorms and hot, windy conditions that might lead to increased fire growth on Sunday as they worked to preserve distant towns.

The McKinney Fire was out of control in Northern California's Klamath National Forest on Sunday, with thunderstorms looming just south of the Oregon state border, according to US Forest Service spokesperson Adrienne Freeman.

“The fuel beds are so dry and they can just erupt from that lightning,” Freeman said. “These thunder cells come with gusty erratic winds that can blow fire in every direction.”

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According to a Sunday incident report, the fire grew to more than 80 square miles (207 square kilometers) in size just two days after igniting in a largely unpopulated area of Siskiyou County. The cause was being investigated.

The fire charred trees along California Highway 96, and the burnt wreckage of a pickup truck sat in a highway lane. Thick smoke blanketed the area, as flames blazed through hillsides near residences. In one neighborhood, where a brick chimney stood surrounded by rubble and burnt automobiles, the fire created an odd orange-brown tone.

A second, smaller fire just to the west that was sparked by dry lightning Saturday threatened the tiny town of Seiad, Freeman said. About 400 structures were under threat from the two California fires. Authorities have not confirmed the extent of the damage yet, saying assessments would begin when it was safe to reach the area.

A third fire, which was on the southwest end of the McKinney blaze, prompted evacuation orders for around 500 homes Sunday, said Courtney Kreider, a spokesperson with the Siskiyou County Sheriff’s Office. The office said crews had been on the scene of the fire since late Saturday but that the fire Sunday morning “became active and escaped its containment line.”

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Several people in the sheriff’s office have been affected by evacuation orders due to the fires “and they’re still showing up to work so, (a) very dedicated crew,” she said. A deputy lost his childhood home to fire on Friday, according to her.

The McKinney fire “remains 0% contained,” the Siskiyou County Sheriff’s Office said in a Facebook post late Sunday night. As the McKinney fire spread, some residents chose to stay behind while others heeded orders to leave.