TAHOE CITY, Calif. — Cooler temperatures and higher humidity assisted with moderating some activity on the Mosquito Fire on Saturday but air quality in the Truckee-Tahoe region is “unhealthy-to-hazardous” Sunday morning.

The Mosquito Fire, burning brush and timber in steep, rugged terrain near Oxbow Reservoir, 4 miles east of Foresthill and due west of the basin, has grown to 41,443 acres and is 10% contained, officials said Sunday morning. As of Saturday night, the fire had consumed 37,326 acres and had no containment.

“Fire activity moderated Saturday night as humidity increased,” Cal Fire said but added that an increase in winds has continued the fire’s spread to the north and northeast. “Smoke and clouds over the fire Sunday should somewhat reduce fire behavior, although the vegetation remains critically dry and is burning readily. Firefighters are taking full advantage of the reduced fire behavior and using direct-suppression tactics as much as they can. Where they are unable to get close to the fire’s edge, they are using indirect tactics, such as using heavy equipment to create new firelines or open firelines from previous fires that have since grown over with brush and trees.”

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Firefighters are building control lines along the area of Foresthill Road and out in front of the head of the fire toward the north and northeast. A spot fire in the area of Chicken Hawk occurred Saturday which firefighters contained with the help of dozers and aircraft.

Fire crews are also tapping into previously used control lines from past fires and a large amount of resources have been working to hold the fire at Volcano Road as well as north of Quintette, Cal Fire said.

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With the increase in fire activity to the east of the communities of Foresthill, several more evacuation orders and warnings have been issued. Cal Fire is expecting more resources to arrive from throughout the state and both fixed-wing and rotor-wing aircraft continue to assist ground crews as flying conditions allow.

Evacuation orders and warnings for Placer County can be found here.

Evacuation orders and warnings for El Dorado County can be found here.

Overall, there are 1,792 personnel fighting the blaze that is threatening approximately 5,848 structures and has forced 11,117 to evacuate.

Cal Fire’s Interagency Incident Management Team 5, and Placer County Sheriff’s Office are in unified command.

The Mosquito Fire’s cause remains under investigation. Pacific Gas & Electric said unspecified “electrical activity” occurred close in time to the report of the fire on Tuesday, according to the Associated Press.

The National Weather Service on Sunday said degraded air quality will persist in the Truckee-Tahoe region. 

“While minor improvement is possible by late morning due to low level mixing, smoke modeling depicts another swath of smoke moving in once again across the Tahoe Basin and Sierra Front late this afternoon and evening which could worsen air quality and reduce surface visibility to around 1-3 miles,” the weather service said. “Overall, not a good time to be outdoors.”

The service is also forecasting showers between 11 a.m. and 2 p.m. and then thunderstorms join the mix after 2. The chance of precipitation is 40% with a high temperature of 79.

The chance of thunderstorms continues overnight and into Monday with lesser chances in the evening into Tuesday.

Bill Rozak is editor for the Sierra Sun. He may be reached at brozak@swiftcom.com.