Map of the 6-5 Fire. Areas highlighted in red are under mandatory evacuation orders. Screenshot of the map was taken on Sept. 3, at 8:40 a.m. ET.

Firefighters are battling a series of wildfires that erupted in north-central California after thousands of lightning strikes were reported in the region, prompting evacuations and scorching buildings in a historic Gold Rush town.

The TCU September Lightning Complex has burned over 20 total square miles in Calaveras, Tuolumne, and Stanislaus counties as of Sept. 3, according to the California Department of Forestry and Fire Protection (Cal Fire). The complex comprises at least 22 "distinct fires" that ignited on Sept. 2 after dry thunderstorms moved into California.

More than 630 firefighting personnel were assigned to the complex, which continued to burn in the Sierra Nevada foothills without any containment, Cal Fire said. The agency said fire crews were challenged by weather conditions as gusty winds lingered in the region from nearby thunderstorm cells.

"The fire has exhibited active runs in critically dry tall grass, brush, and timber fuels," Cal Fire said in a statement. "The terrain is challenging to access, requiring fire crews to hike in by foot to many remote locations."

The largest of the fires within the complex was the 6-5 Fire that had scorched more than 10 square miles in Tuolumne County and threatened the last remaining structures in Chinese Camp, a small town and historical landmark located about 40 miles from Yosemite National Park. The fast-moving fire forced the evacuation of the entire town and surrounding areas.

Cal Fire said the complex has damaged and destroyed a "number of structures," adding that a damage inspection team is on order. The agency warned that multiple communities in the region were at risk, including ancestral tribal lands, and various evacuation notices remained in place.

The series of fires comes after nearly 4,800 total lightning strikes, concentrated in areas between the inland East Bay and the Central Valley, were recorded between midnight and 5:30 a.m. local time Sept. 2, according to the National Weather Service. The combination of dry lightning and dry vegetation increased the risk of wildfires in the region.

TCU September Lightning Complex

The largest of the fires in the TCU September Lightning Complex includes the 6-5, 2-2, 2-8, 6-2, and 2-7 fires, according to Cal Fire. The agency said the fires remained active on Sept. 3 with zero containment.

The fires, which were burning at a "dangerous rate of spread" and threatening multiple structures, led to mandatory evacuation orders with widespread warnings extending further, Cal Fire said. The fires also led to the closure of parts of nearby highways.

On Sept. 2, California Gov. Gavin Newsom's office announced that the state secured a fire management assistance grant from the Federal Emergency Management Agency to support firefighting efforts.

"The TCU September Lightning Complex fires ignited the morning of Tuesday, September 2, 2025 as part of a statewide storm that saw more than 9,000 lightning strikes," Newsom's office said in a news release. "The 2-7 fire is actively burning in Calaveras and Tuolumne counties with several communities threatened in Calaveras County."

More than 300 residents in the area were already under evacuation orders while an additional 1,400 were under evacuation warnings, according to Newsom's office.

What is Chinese Camp?

As the 6-5 Fire continued to threaten Chinese Camp, the Cal Fire Tuolumne-Calaveras Unit said Sept. 3 that firefighters were focusing on building containment lines and strengthening lines that have already been established.

Several homes were damaged or destroyed by the fire in Chinese Camp, according to NBC News and local television station KCRA. Meanwhile, the Chinese Camp School remained untouched by the flames, according to the Cal Fire Tuolumne-Calaveras Unit.

KCRA reported that the fire destroyed the town’s historic post office building. The stone and brick post office, built in 1854, had been operating until it was burned down, according to California State Parks.

Chinese Camp was a California Gold Rush town where Chinese miners, driven out of a nearby camp, settled around 1850, Visit Tuolumne County states. The county's tourism website says that the rural town was once home to about "5,000 Chinese miners in addition to as many Americans and Europeans."

"Chinese Camp was headquarters for stagelines in early 1850s and for several California Chinese mining companies," according to California State Parks. "Much surface gold was found on hills and flats."

What is dry lightning?

Dry lightning occurs during "dry thunderstorms," which produce little to no rainfall. On Sept. 2, across California, the rain evaporated in dry air before reaching the ground, according to the weather service, adding: "Most areas saw less than 0.10 inches of rain & there were a few fire starts."

Wildfires are a real concern with dry lightning. According to the weather service, the drier the storm and the drier the vegetation, the more likely lightning strikes are to spark wildfires. That's because cloud-to-ground lightning can easily ignite parched fuel without rain to help dampen it.

On Sept. 3, Cal Fire reported that more than 110,000 lightning strikes were recorded in August — sparking over 530 wildfires. Those lightning-caused fires burned a total of 45 square miles, according to the agency.

"We are currently seeing increased fire activity due to the lightning activity seen over the last few days, and conditions remain critical," Cal Fire said in a statement. "Please stay prepared, stay aware, and have a plan in case a wildfire threatens your community."

See wildfire map

Contributing: Doyle Rice, USA TODAY

This article originally appeared on USA TODAY: Lightning-caused wildfire prompts evacuations, burns historic California gold mining town

Reporting by Julia Gomez and Thao Nguyen, USA TODAY / USA TODAY

USA TODAY Network via Reuters Connect