August On the early morning of August 17, thunderstorms carried northward from the weakening
Tropical Storm Fausto moved across Glenn and Mendocino Counties, starting at least 13 fires. By 5:00 pm
PDT, the Doe Fire in Glenn County north of
Willows had grown to , and firefighters had arrived on the scene. Most of the fires were on the Grindstone Ranger District with one on the Covelo Ranger District, ranging in size from . Thunderstorm activity continued for another couple of days, igniting even more wildfires on August 17. On the morning of August 17, the Elkhorn Fire was ignited north of the Doe Fire and east of the Hopkins Fire, near Maple Creek, in Tehama County, which was separate from the August Complex at the time. By 11:00 am PDT on August 17, five fires had been contained, while the Doe Fire had grown to . In addition, the Box Fire in the
Snow Mountain Wilderness reached , and the Rockwell and Pine Kop Fires west of
Elk Creek had burned and respectively. Aided by thunderstorm activity and strong winds, the fires expanded rapidly throughout the day, and more fires were discovered bringing the total to 20. Forest Service officials decided to manage these fires as one incident, the August Complex. On the morning of August 18, the Doe Fire was estimated at , while the Rockwell and Pine Kop fires were at each. The Box Fire had been mostly contained and held at . Over the next two days, hot dry weather and gusty winds caused the fires to explode in size. Additional fires were discovered, increasing the total to 35. By the morning of August 20, the fires had burned and were advancing downslope to the east. In Glenn County, evacuation orders were issued for parts of Elk Creek,
Chrome, Burrows Gap, and
Red Mountain, and an evacuation warning for
Grindstone Rancheria. In the afternoon, the complex had grown to . All of Glenn County west of County Road 306 was placed under an evacuation order. On August 21, due to continued high fire danger, the Mendocino National Forest was temporarily closed to all public access. By August 24, two additional fires were identified, bringing the total number of new fires to 37 and overall acreage to . At this point, some of the larger fires had burned together. The Doe Fire absorbed the Rockwell and Pine Kop fires and was at . By August 27, the complex had increased in size to . The Doe Fire had expanded to and was 31 percent contained, as firefighters successfully stopped the fire from advancing further east and were building a containment line to the west. There was little containment on the Tatham Fire, now at , the Glade Fire, now at , and the Hull Fire, which was at . On August 28, the complex's total area had increased in size to , and was 18 percent contained. On August 29, the Doe Fire absorbed the Tatham Fire, while the Hopkins Fire had spread east into the
Shasta-Trinity National Forest. The Doe Fire was now 52 percent contained, though the complex overall remained at 18 percent, as the other fires continued to spread. A heat wave combined with extremely smoky conditions hampered aircraft operations. On August 30, the Doe Fire also absorbed the Hull and Glade Fires, making the complex essentially one large fire, with the exception of the Hopkins Fire to the north. There were 607 personnel committed to the fire; crews stopped flames from advancing further south towards
Lake County, but the fire continued to burn largely uncontrolled to the west. A containment line was being constructed west of the Glade Fire, in the vicinity of the
Black Butte River and Bald Mountain.
September On September 1, the complex had increased to , most of that in the combined Doe-Glade-Tatham-Hull fire, and was 20 percent contained. Firefighters were building containment lines along the west side of the Doe Fire and the south side of the Hull Fire. The Hopkins Fire had expanded to with no containment. One firefighter was confirmed dead in a vehicle accident, and another was injured. Over the next few days, the fire continued to expand rapidly, burning about a day, reaching on September 4. Crews conducted
back burns west of the Tatham Fire and northwest of the Hull Fire. Increased fire activity in eastern Mendocino County led to an evacuation warning for the Mendocino National Forest, north of Hull Mountain. On September 5, the
National Weather Service issued a Fire Weather Warning due to high winds and unseasonably hot temperatures of . On September 6, aircraft dropped water and retardant on the Hopkins Fire, which had expanded to . Back-burns were conducted on the northwest side of the Doe Fire, in anticipation of extreme wind conditions. By September 7, the complex had increased in size to and was 24 percent contained. A total of 1,138 personnel were working on the fire. On September 8, evacuation orders remained in place for western Glenn County and eastern Mendocino County, and had been expanded to parts of northern Lake County. Strong
Diablo winds continued to drive fire activity, but helped clear smoke westward, allowing for increased aircraft operations. During September 8–9, the fires grew rapidly, driven by strong east winds. The complex increased in size to , with the Hopkins Fire accounting for . On September 9, the Elkhorn Fire merged with the Hopkins Fire, and the combined fire was assigned to the Elkhorn Fire incident and no longer managed as part of the August Complex. On September 10, the August Complex jumped containment lines on the southwest, crossing the Black Butte River and moving into the
Yuki Wilderness, triggering evacuations in Lake County, north of
Lake Pillsbury. On the morning of September 10, the August Complex was estimated at , making it the largest fire complex in California history, surpassing the 2018
Mendocino Complex Fire, which had burned in the southern part of the Mendocino National Forest. , as seen on September 8 On September 10, the combined Elkhorn and Hopkins Fires were being managed jointly as the Elkhorn Fire, which had burned . The fire rapidly advanced into the
Six Rivers National Forest, jumping the canyons of the
Mad River and
North Fork Eel River, before crossing the
Eel River south of
Alderpoint. Evacuations were ordered in
Humboldt County from
Bridgeville south to
Fort Seward and Alderpoint, while areas from there west to
U.S. Highway 101 received an evacuation advisory. On the morning of September 11, the Forest Service was continuing to manage the two fires as separate incidents within the larger complex, due to the immense size of the complex's burn area. The Doe Fire in the August Complex was officially referred to as the "August Complex South Zone", which was and 25 percent contained, while the Elkhorn Fire was being managed as the "August Complex North Zone", which was still at and 27 percent contained, giving the overall complex an area of and 25 percent containment. The western portion of the Elkhorn Fire was further designated as the "August Complex West Zone", which was managed by
CAL FIRE. Due to the rapid fire spread and thick smoke in the area, officials had trouble estimating the actual size of the fire. On September 13, the fire was thought to have reached . By September 15, the burn area had been revised to , as better mapping data became available. On the North Zone, the fire continued advancing north, jumping the
South Fork Trinity River and advancing towards
State Route 36. Firefighters were working to save homes around the Ruth Lake area. On September 16, it was reported that 35 structures were destroyed, and 400 were still threatened. On the South Zone, the fire continued spreading through the Yuki Wilderness and
Sanhedrin Wilderness. On the North Zone, firefighting efforts were focused on stopping the advance north of the South Fork Trinity River. On September 18, evacuations were lifted in the Glenn County portion of the Mendocino National Forest, as the eastern flank of the fire was almost fully contained. On September 19, some evacuations in Mendocino County were also downgraded to an evacuation warning. Firefighters conducted back-burns west and northwest of Lake Pillsbury. The entire August Complex was at and was 31 percent contained, with the fire spreading on its southwestern flank. By September 21, a significant portion of the large, previously-unburned section of the Yolla Bolly-Middle Eel Wilderness between the North and South Zones had been burned over. In Trinity County, evacuation orders were in effect for the communities of
Ruth,
Forest Glen,
Post Mountain, and Trinity Pines, as the North Zone continued advancing towards State Route 36. Additional crews were sent in an effort to prevent the fire from crossing the highway. On the South Zone, firefighters had made considerable progress halting the advance near Lake Pillsbury. On the West Zone, the fire continued to threaten Humboldt County. More than 2,000 personnel were assigned to the West Zone at this time. On September 24, members of the California National Guard were also deployed to the West Zone. The entire August Complex was at and 38 percent contained. Evacuation orders were issued in Trinity County from Ruth Lake and
Mad River west to the Humboldt County line. Evacuation warnings were also issued for Humboldt County from Alderpoint east to the Trinity County line. On the South Zone, the fire held within containment lines at Lake Pillsbury, but evacuation orders remained in place in nearby areas of Mendocino and Lake Counties. On September 29, the entire August Complex had grown to , and was 43 percent contained.
October On October 1, the August Complex had grown to , with containment increasing to 51 percent. On October 5, the August Complex had grown to , with containment at 54 percent, with the majority of the growth coming from the northwestern and northeastern flanks of the fire. This made the August Complex the first "gigafire" (a fire spanning over a million acres) in the modern history of California. Due to an ongoing
La Niña event, California got less rainfall than usual, and the rainy season started later than would typically be seen in October. This made difficult conditions for firefighters and extended the fire season.
November After a couple of small rain events and favorable weather, firefighters and aircraft were able contain most of the fire by mid-November, with over 95% containment reported on November 9. Trinity County Environmental Health officials warned that the fire could potentially have contaminated ground and surface water in certain areas affected by the fire. They warned not to drink water from the area, noting that boiling water does not remove contaminants. On November 12, the Forest Service reported that the August Complex had finally reached 100% containment, with the combined incident management being disbanded that same day. ==Growth and containment==