A wildfire that has burned through more than 5,000 acres of forest on the eastern boundary of Mendocino County halted its advance Friday, but firefighters warned residents in rural hamlets on the boundaries of the blaze to prepare for the possibility of evacuations if the flames resume their march.

The fire, sparked by dry lightning strikes July 30 outside Laytonville, unleashed a billowing tower of smoke that was moving south and threatened to cloud the skies over Sonoma and Napa counties this weekend. Air quality officials issued an alert Friday warning North Bay residents to take precautions to limit their exposure to smoke.

By Friday evening, the so-called Lodge Complex fire had scorched 5,400 acres and threatened 35 structures, including cabins and homes, Cal Fire officials said. Officials stopped short of ordering mandatory evacuations Friday, but warned people within the affected areas to have a plan and be prepared to evacuate if necessary. The warning covers areas near Camp Seabow, Bowman Ranch Road, Peterson and Grubb creeks and property in the surrounding residential areas, including Big Bend, Cedar Flat, Dann Valley, Cummings, Grizzly Creek, Hermitage, Little Dann Creek and Tan Oak Park.

Firefighters had contained about 30 percent of the fire.

Firefighting has been difficult because of the thick brush, dry conditions and steep, uphill terrain, officials say. But firefighters sought to hold the blaze at the Eel River and by Friday they had been able to do that, except in two areas toward the East.

As of Thursday night, the blaze was burning toward Leggett and was still several miles out. Residents and business owners mostly reported business as usual in the small town, which is about 17 miles northwest of Laytonville and known for its towering redwood trees and the Chandelier Drive-Thru Tree and Park, a popular tourist attraction.

While some said they had seen fewer tourists earlier in the week, visitors began to stream in toward the end of the week.

“Skies are blue and we’re full this weekend,” said Sandy Harrison, part owner of the Redwoods River Resort and Campground in Leggett, who said she attended one of Cal Fire’s daily briefings on Thursday. “I left that meeting and thought ‘whew.’ They seemed to be confident they were going to hold the line on it.”

Harrison said she has spoken to visitors who said they saw haze and smoke as they headed to Leggett from the south and east.

“They’re just driving through it,” she said.

Confusion Hill, another tourist spot located in Percy, also reported few effects from the fire.

“We’ve had a steady amount of people yesterday and more today,” said manager John Mills. “Right now, I can’t even see the fire from here.”

Cal Fire has been using Big Bend Lodge, which is on the South Fork of the Eel River, as a staging area for firefighters, engines, helicopters and other equipment since the third day of the fire, said John Evans, the manager. He added though, that owners were so concerned in the early days of the blaze, that they asked their guests to leave.

“We just thought we needed to get people out,” he said. “We’re here, but all of the neighbors are in close communications and I can tell you we are doing some radical clearing.”

Evans said the lodge sits in a valley just below a thickly-wooded ridge, one of the few places firefighters have been able to get access to the fire.

“We’ve been able to see black plumes of billowy smoke,” said Evans, over the sound of a helicopter “It looks closer than it is. But we’re ready if we have to go.”

Cal Fire has reported three injuries since Thursday morning but did not provide details. Officials said 1,889 people were helping to battle the flames, and the cost for the effort totaled $9 million.

Bay Area Air Quality Management issued a smoke advisory Friday, warning residents of Sonoma and Napa counties that smoke was moving southward in amounts that could impair air quality. It advised residents to:

— Reduce exposure to smoky air by remaining indoors with windows and doors closed

— Set air conditioning units and car vent systems to re-circulate

— If air smells of smoke, limit outdoor activities to avoid unnecessary exposure.

— If you have asthma or other lung disease, make sure you follow your doctor’s directions about taking your medicines and following your asthma management plan. Call your doctor if your symptoms worsen.

— If you have heart or lung disease, if you are an older adult, or if you have children, talk with your doctor about whether and when you should leave the area.