Firefighters battle hot, dry conditions in Northern Calif. fire

SAN FRANCISCO — Firefighters were making progress on extending containment lines on the largest wildfire in California history, though unhealthy ozone levels caused by smoky conditions and 90-degree temperatures will challenge crews through the weekend, fire officials said Saturday.

The Mendocino Complex, comprising the Ranch Fire and River Fire, grew slightly overnight on the northern edge and reached 331,770 acres.

It was 77 percent contained by Saturday, according to the Cal Fire. The blazing fires in Northern California have worsened air quality in the Bay Area, prompting officials to declare the eighth air quality alert of the year for Sunday.

Officials with the Bay Area Air Quality Management District announced the alert Saturday, advising residents that ozone pollution is forecast to reach unhealthy levels Sunday because of a mixture of wildfire smoke, exhaust emanating from vehicle tailpipes, and warm temperatures.

“The smoke from the wildfires in California, Oregon and British Columbia is exacerbating the poor air quality,” said Kristine Roselius, a spokeswoman for the air district.

“As the temperatures get hotter, the air quality declines, so that’s when we’ll see the worst air quality of the day” Sunday.

Firefighters working on the fire line will face declined air quality due to fine particulate matter in the air, Roselius said.

A high-pressure system over the blaze is creating smoky and hazy conditions for crews on the ground and in the air, said Idamis Del Valle, a meteorologist with the National Weather Service.

“It’s still going to be warm and dry for crews at the Mendocino Complex fire,” Del Valle said Saturday. “Smoke and haze will increase today because of that system, but there won’t be any strong, gusty winds.”

Cal Fire officials said heavy smoke is making it impossible for fixed-wing aircraft to navigate, but Del Valle said another weather system is expected to push through Sunday afternoon and last into next week, which she said should clear out much of the smoke and haze.

In the meantime, crews are planning to take advantage of an inversion layer of smoke that clears midafternoon to fly aircraft over the blaze and drop retardant.

Crews have been mopping up and constructing containment lines on the northern portion of the Mendocino Complex Fire, officials said.

“On the southern portion of the fire, suppression repair efforts will continue throughout the day,” Cal Fire said. “Firing operations will continue as weather conditions and fuel moistures allow.”

Roughly 3,470 fire personnel are working to extinguish the Mendocino Complex, which is expected to be fully contained by Sept. 1.