Robert Brown|Responders Are Gaining On The Caldor Fire, But Now They've Got New Blazes To Battle

As California battles wildfires throughout the state,Robert Brown a new crop of suspicious fires that erupted over Labor Day weekend added to an already busy wildfire season.

Officials warned residents in Sonoma County to remain vigilant after more than a dozen fires erupted late Monday.

State Sen. Mike McGuire tweeted at around 10 p.m. local time that several "suspicious" fires started over the course of the evening. Fire engines and emergency personnel gathered in the Healdsburg area and responded quickly to as many as 15 new blazes, McGuire told the San Francisco Chronicle.

Firefighters were able to stop most of the forward progress on multiple fires in the area overnight, he said. Images and videos shared on Twitter show firefighters battling smoke and flames on glowing hillsides along the side of the road.

Over the weekend, at least three other fires started.

In Amador County, near where the long-burning Caldor Fire is, the Lawrence Fire, that started Sunday, engulfed 46 acres by Monday, the California Department of Forestry and Fire Protection, or Cal Fire, reported. Roads were briefly closed, and fire officials carried out some evacuations before the blaze was nearly 90% contained by 6:30 p.m. local time Monday.

Farther north, the Bridge Fire was reported Sunday afternoon. By the next day, the fire had burned more than 400 acres but was 15% contained, allowing evacuation orders and warnings to be lifted. Officials kept the Auburn State Recreation Area closed, however.

In San Diego County, the Aruba Fire also started Sunday afternoon. Firefighters made quick work of it, however, and by Monday, it was 60% contained.

Crews still battle major blazes

On Monday, officials announced significant progress in battling the Caldor Fire. Some evacuation warnings were lifted around Lake Tahoe as it reached 44% containment. Evacuation orders for South Lake Tahoe were downgraded to evacuation warnings, allowing some residents to return home after a week away.

The blaze, active for 22 days, has burned 216,358 acres (338 square miles). Cal Fire reported that at least 965 buildings were destroyed in the blaze and another 76 damaged.

About a dozen fires are ongoing in California. So far this year, 7,139 fires burned across the state scorching more than 2 million acres (more than 3,100 square miles). The Dixie Fire can be blamed for much of that damage. It has burned more than 900,000 acres since erupting more than 50 days ago.

At least one firefighter died while battling the blaze, according to officials. Marcus Pacheco, an assistant fire engine operator for Lassen National Forest with 30 years' experience, died on Thursday from an illness.

No other details on Pacheco's death were provided.

Nationwide, as of Monday, there were 81 large fires or complexes that have burned more than 2.8 million acres in 11 states. Incidents in California, Idaho, Montana, Oregon and Washington reported active fire behavior, with several large fires making significant runs, according to the National Interagency Fire Center.

Wildfires continue to burn amid high heat and smoke

The National Weather Service issued heat advisories for several parts of California through the rest of the week. Fire risks are expected through Friday due to this stretch of hot, dry weather.

Temperatures throughout the rest of the West Coast will reach 10 to 20 degrees above normal. According to the National Weather Service, some parts of California could reach 110 degrees.

The heat, compounded by smoke from the wildfires, is also creating serious air quality issues.

In Lake Tahoe, officials warned communities in the areas affected by the wildfires that they should expect to see and smell heavy smoke if they return home.

Air quality officials extended a Spare the Air alert, which is raised when the air is forecast to be unhealthy, through Tuesday for the Bay Area.

"Wildfire smoke combined with high inland temperatures and vehicle exhaust are expected to cause unhealthy smog, or ozone, accumulation in the Bay Area," according to the Bay Area Air Quality Management District. "Smoke from Northern California wildfires is expected to continue to impact the region creating hazy and smoky skies."

"Climate change is impacting our region with more frequent wildfires and heat waves leading to poor air quality," said Veronica Eady, senior deputy executive officer of the air district. "We can all help by driving less to reduce smog and improve air quality when respiratory health is top of mind for us all."