TL;DR: The Lucas Fire reached 4,008 acres with 15% containment near Potter Valley on September 12, 2026, with evacuations, highway closures and Red Flag winds shaping backcountry decisions.

Fire footprint on September 12

The Lucas Fire grew to 4,008 acres near the rural Mendocino County community of Potter Valley and the Lake County line on Saturday, according to The Mendocino Voice. The same update placed containment at 15% on Saturday night.

The progression was rapid. The fire was first reported at about 10 acres on Thursday morning, according to The Mendocino Voice. By Friday morning it was more than 1,000 acres. By Thursday night it had spread to 1,099 acres and was 5% contained.

Morning mapping on Saturday showed 3,466 acres and 15% containment, according to The Press Democrat. The fire’s size increased to 3,846 acres by 3 p.m. Saturday, according to The Press Democrat. A later Saturday update listed 4,008 acres, according to The Mendocino Voice.

Fire behavior pushed toward the southeast on Saturday afternoon, according to Action News Now. The Lucas Fire was burning to the north of Witter Springs in Lake County, according to Action News Now. Northwest winds increased fire activity on the eastern side of the fire, according to Action News Now.

Start time, command and cause status

The wildfire started at 9:18 a.m., according to The Mendocino Voice. The initial report described about 10 acres on Thursday morning.

The fire broke out Thursday morning just after 9 a.m., according to ABC7 San Francisco. It was burning in a remote location with difficult access, according to The Mendocino Voice.

The agency with jurisdiction over the fire transferred from CAL FIRE Mendocino Unit to CAL FIRE Sonoma-Lake-Napa Unit, according to Action News Now. The North Bay Type 3 Incident Management Team was at the scene helping support CAL FIRE Sonoma-Lake-Napa Unit with operational, support and logistical functions, according to Action News Now.

The cause was under investigation, according to The Mendocino Voice. Firefighters faced conditions Friday afternoon that included high temperatures and strong winds, according to The Press Democrat. The wildfire was plausibly started by lightning, but the cause remained under investigation, according to The Press Democrat.

Red Flag weather and smoke exposure

A Red Flag Warning was in effect through Monday afternoon due to strong winds and elevated fire weather conditions, according to The Mendocino Voice. A Red Flag Warning for the area remained in effect through Monday afternoon due to strong winds and elevated fire weather conditions, according to Action News Now.

National Weather Service Meteorologist Jacob Boomsma said Saturday morning that firefighters were facing a critical fire weather day with dry conditions, relatively low humidity and wind gusts expected to reach 30-35 mph in higher terrain, according to The Press Democrat. Boomsma said Lake County is a wind-prone area and conditions where the fire was located were particularly windy, according to The Press Democrat.

A Red Flag Warning was also in effect in Lake County Saturday morning through late Saturday night due to heat and winds, according to The Press Democrat. Firefighters focused on strengthening containment lines in anticipation of forecast weather, according to Action News Now.

Cal Fire officials said in a 6:52 a.m. incident report that resources were focusing on strengthening containment lines in anticipation of forecast weather, according to The Press Democrat. A cooling trend expected Saturday night and Sunday should aid firefighters, with temperatures in the burn area forecast to drop into the 70s alongside higher relative humidity, according to the National Weather Service as reported by The Press Democrat.

Smoke from the fire could be visible in Lake County and surrounding communities, impacting air quality, according to The Mendocino Voice. To check current air quality and wildfire smoke conditions, the public was directed to airnow.gov/wildfires, according to The Mendocino Voice.

Evacuation orders for backcountry residents

Evacuation orders and warnings were issued by Mendocino County and Lake County, according to The Mendocino Voice. Immediate evacuation orders remained in place for multiple zones.

As of Saturday morning, zones under evacuation orders in Lake County were MNF-E016, MNF-E018, MNF-E019, UPP-E023, UPP-E025, UPP-E026, UPP-E027 and UPP-E030, according to Action News Now. In Mendocino County, zone MEN-2POT08-B was under evacuation order, according to Action News Now.

The community of Witter Springs, located in Zones UPP-E027 and UPP-E030, was under evacuation orders due to proximity of the fire, according to Action News Now. The Mendocino County Sheriff’s Office issued an evacuation order Thursday afternoon for the Potter Valley area as the fire spread to 200 acres, according to The Mendocino Voice.

Residents advised to be ready to evacuate were told to gather belongings, check on neighbors and leave early if possible, according to The Mendocino Voice. To find what zone applied, residents could visit mendoready.org or protect.genasys.com, according to The Mendocino Voice. People could know their zone by visiting the Genasys Protect website, according to Action News Now.

Evacuation warnings and shelter locations

Evacuation warnings covered additional Lake and Mendocino county zones on Saturday morning. In Lake County, warning zones were MNF-E012, MNF-E013, MNF-E015, MNF-E017, MNF-E021, UPP-E028, UPP-E031, UPP-E032, UPP-E035 and UPP-E038, according to Action News Now. In Mendocino County, warning zones were MEN-2POT08-A and MEN-2UKV28, according to Action News Now.

An evacuation center staffed by the American Red Cross was set up at Lake County Fairgrounds - Fritch Hall, located at 401 Martin Street in Lakeport, according to Action News Now. Friday evening, the temporary evacuation point at the Lake County Fairgrounds transitioned to an official evacuation shelter staffed by the American Red Cross Northern California Chapter at Fritch Hall, according to The Press Democrat.

Small animals were welcome but were to be housed in a separate building and owners were responsible for care, according to fire officials as reported by The Press Democrat. The animal evacuation center was established at the Baldwin Pavilion of the Lake County Fairgrounds, according to Action News Now.

San Francisco firefighters were dispatched to help battle the wildfire, according to The Mendocino Voice. About 1,300 personnel were assigned to the fire Saturday night, according to The Mendocino Voice. About 1,000 personnel were assigned as of Saturday morning, including air tankers and helicopters, according to Action News Now.

Aircraft, dozers and line construction

Numerous firefighting air tankers from throughout the state were flying fire suppression missions, according to The Mendocino Voice. Multiple firefighting aircraft were working the fire, dropping water and fire retardant and providing real-time intelligence to command staff, according to Action News Now.

During overnight hours, five nighttime helicopters carried out suppression operations, according to Action News Now. With call letters Nine Charlie Hotel, a Chinook helicopter dipped out of the Scotts Creek wetlands near Upper Lake for return runs to the fire Friday, according to The Press Democrat.

Crews on the ground were engaged in suppression efforts and construction of direct control lines where favorable, according to Action News Now. Firefighters continued efforts to strengthen containment lines while the fire remained within established control objectives, according to Action News Now.

The Lucas Fire encroached on Hunters Point, damaging critical communication infrastructure above Bachelor Valley on Friday, according to The Press Democrat. As the fire advanced on the peak, several bulldozer operators fell back to a safety zone and allowed the fire to pass, according to The Press Democrat. Air support was called in, but the peak was too smoky to make retardant drops, according to The Press Democrat.

Firefighters attempting to protect communication antennas for Lake County retreated to a temporary refuge when conditions became unsafe, until it was safe to reengage, according to The Press Democrat. Due to increased fire activity and conditions in the area, some communications equipment was damaged, according to The Press Democrat.

Forest closure and highway shutdowns

The Mendocino National Forest ordered an emergency closure for a portion of the Upper Lake Ranger District, according to The Mendocino Voice. Campgrounds within the closure area included Middle Creek, Penny Pines and Deer Valley, according to The Mendocino Voice.

The closure covered national forest roads, trails and campgrounds within a boundary running east along Forest Road 16N30 from Sam Alley Ridge, north along 16N01 and Elk Mountain Road and west along McCreary Glade Road back to the forest boundary, according to The Mendocino Voice. Off-highway vehicle trails closed included 01, 05A, 07, 10 and 15, according to The Mendocino Voice.

State Highway 20 was closed at Bachelor Valley Road, Witter Springs Road and Saratoga Springs Road, according to The Mendocino Voice. Temporary closure points were active at Highway 20 and Bachelor Valley Road, Highway 20 and Witter Springs Road, and Highway 20 and Saratoga Springs Road, according to Action News Now.

Highway 20 road closures were in effect at Bachelor Valley Road, Witter Springs Road and Saratoga Springs Road on Saturday, according to The Press Democrat. Road closures were also active at Highway 20 and Bachelor Valley Road in a separate Sunday-morning incident summary, according to NBC Bay Area.

Community briefing planned for Upper Lake

A community meeting to update residents was scheduled for 6 p.m. Sunday at Running Creek Casino, 635 State Highway 20 in Upper Lake, according to The Mendocino Voice. The meeting was to discuss fire activity, suppression efforts and evacuation considerations, according to The Mendocino Voice.

The meeting was to include representatives from Cal Fire’s Sonoma-Lake-Napa Unit, the Lake County Sheriff’s Office, Mendocino National Forest, Lake County government officials and emergency management personnel, according to The Mendocino Voice. The meeting was to be livestreamed at a listed YouTube live address, according to The Mendocino Voice.

Sources referenced