A wildfire has burned across the Sierra Nevada mountain range for the first time in recorded history, according to a leading California official.

Cal Fire Director Thom Porter said on Wednesday the Dixie Fire is the first fire that has made it from Sierra Nevada’s western slopes to the floor of the eastern valley, the San Francisco Chronicle reported.

Firefighters have been battling the fire for more than a month as it has burned more than 662,000 acres and destroyed more than 1,000 structures.

Thousands have had to be evacuated across the state, and firefighters are currently working to save the city of Susanville, home to 18,000 people.

People have been sheltering in gyms, tents, RVs and other places across the state as they wait to be allowed back to their homes, the Chronicle noted.

California has been devastated this wildfire season, with multiple blazes burning across the state at one time.

Pacific Gas & Electric shut off power to more than 50,000 residents Tuesday to prevent more fires from forming. 

Windy conditions have allowed the wildfires to grow, with fire behavior analyst Brian Newman saying Wednesday the same windy conditions will occur Thursday and this weekend.