If you’re planning to leave the Santa Clarita Valley this week, you may want to think twice about spending too much time outdoors because of the air quality.

Air quality across much of Los Angeles County is expected to remain unhealthy over the next several days as smoke from the still-burning Boyle Heights warehouse fire combines with a humid heat wave moving into Southern California.

The worst air quality is expected in areas south of Santa Clarita, including the San Fernando Valley, the Los Angeles Basin, the San Gabriel Valley and parts of the Inland Empire, according to Devin Black, a meteorologist with the National Weather Service in Oxnard.

The smoke is coming from a massive fire that broke out Wednesday, June 17, at a 500,000-square-foot cold food storage warehouse in Boyle Heights. Nearly a week later, the fire continues to smolder, sending a large plume of smoke high into the sky and carrying pollutants miles away from the scene.

“This is a very unique fire, a very unique challenge for the Los Angeles Fire Department,” LAFD Chief Jaime Moore said during a news conference.

Moore said the building is essentially acting like a giant freezer. Its steel walls are packed with thick foam insulation that continues to burn deep inside the structure, making it difficult for firefighters to fully extinguish the fire.

The facility housed approximately 85 million pounds of frozen food and relied on ammonia refrigeration systems to keep products cold. Helicopters have continued dropping water on the building as crews work to cool hot spots buried within the insulated walls.

As smoke from the fire lingers, another factor is expected to make air quality worse: humidity.

Black said a three-day heat wave arriving Tuesday through Thursday will bring monsoonal moisture into Southern California, increasing humidity levels and allowing pollutants to remain trapped in the atmosphere longer.

“Particle pollution can have bad effects,” Black said, noting that children, older adults, pregnant women and people with heart or lung disease are especially vulnerable. Exposure to poor air quality can trigger breathing problems, bronchitis and, in some cases, increase the risk of heart attacks.

Even healthy people can feel the effects after spending extended periods outside.

Health officials recommend staying indoors when possible, keeping windows and doors closed, avoiding whole-house fans or swamp coolers, and skipping candles, incense and fireplaces to help keep indoor air clean.

While Santa Clarita is expected to avoid the worst of the pollution, residents heading to other parts of Los Angeles County for work, appointments, sporting events or summer activities should be prepared for hazy skies and unhealthy air.

A cooling trend is expected to arrive Friday, which forecasters say should help improve air quality heading into the weekend.

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