The thick blanket of smoke pouring into the Los Angeles Basin from two brush fires in the Angeles National Forest is expected to linger through the weekend, prompting health warnings and halting some school athletic programs.
The smoke from a fire north of Azusa that began Tuesday and a blaze above La Canada Flintridge that broke out Wednesday resulted in unhealthy air pollution levels in the San Gabriel Valley as well as parts of Los Angeles.
Weather experts blame weak winds -- which actually prevented the fires from burning more intensely -- for keeping the smoke from dissipating.
"The L.A. Basin is a big cul-de-sac. To the north and the east we're bounded by some pretty high mountains," said Bill Patzert, a climatologist with the Jet Propulsion Laboratory in La Canada Flintridge. "The basin is just filling up with this smoke."
He said the smoke would probably remain until Sunday, along with a high-pressure system that has brought sizzling temperatures and red-flag fire conditions.
"We're sitting in the smoke until Sunday. It's going to get hotter and smokier," Patzert said.
With temperatures expected to reach into the triple digits this weekend, Pasadena Mayor Bill Bogaard said he's worried about the days ahead. "This is going to be a difficult and a long weekend," he said.
Residents around the basin were trying to cope.
In Monrovia, maintenance worker Fernando Zanelli left strict instructions with his children when he left his home Wednesday: No one was to open the windows.
"I was feeling the smoke, and when I woke up I saw black ashes flying in the area," Zanelli said. "I worry about my children breathing in that stuff."
In the gated community of Mountain Cove in Azusa, where a mass of gray smoke tinged with burnt sienna rose high above the 210 Freeway, residents awoke Wednesday morning to the smell of tar. When they walked outside, many found cars were covered in ash.
Real-estate agent Paul Cassatt, 60, who had a heart attack last year and recently had a defibrillator placed in his chest, said he's not taking any chances with his smog-filled environment.
"I'm staying inside," he said.
On Lake Avenue in Pasadena, lunch crowds stayed mostly indoors, and others tried to make their ventures outside as short as possible.
In Chinatown, Winnie Zhou, a cashier at Queen's Bakery, said it smelled like fire when she got ready for work Wednesday morning.
"It was hard to breathe, and I felt like my nose was dry," Zhou said.
Her co-worker, Maggie Alcaraz, said the smoke was worsening the flu-like symptoms she contracted earlier in the week.
"I'm already congested, and it's even worse now," she said. "But I don't even want to breathe in since it's smoky."
Even though most school districts are not yet in session, officials canceled football and band practice and all other outdoor activities.
"The air is dirty. It smells really bad, and the sky is kind of a hazy orange," said Ann Rector, coordinator of health programs for the Pasadena Unified School District.
The Los Angeles Unified School District sent out a memo Wednesday telling administrators to stop outdoor student activities in areas with smoky conditions.
Los Angeles County public health officials warned those with asthma or respiratory problems to stay indoors and advised others to take precautions.
"In all areas of visible smoke or where there is an odor of smoke, all individuals are urged to be cautious and to avoid unnecessary outdoor activities," said Los Angeles County Health Officer Jonathan E. Fielding in a statement Wednesday.
Little Leagues and other outdoor activity groups were advised to cancel practices in areas where there is visible smoke, soot or ash, or where people can smell smoke, he said.
The Morris fire, which grew to 1,700 acres in the Angeles National Forest and was 10% contained, started Tuesday afternoon. On Wednesday afternoon, the Station fire started about 15-20 miles to the west. It had burned at least 20 acres.
Patzert said that on-shore breezes Wednesday afternoon may have made it seem that much of the smoke had cleared. But, he cautioned, during the night or early morning, those breezes reverse and the smoke returns.
"It ebbs and flows," he said. "Breathes in and out."
Cynthia Cervantes McGuire, superintendent of the Azusa Unified School District, said she's concerned about how the smoke is affecting the health of her students.
"We are right up against the foothills, so you can smell it and you can see this thick fog right across the mountains," she said. "It just smells awful."
Times staff writers Alexandra Zavis and Robert J. Lopez contributed to this report.
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Tips for dealing with smoke:
* Keep windows and doors closed -- unless it's extremely hot outside.
* Run the air conditioner if you have one.
* If you have asthma or another respiratory disease, make sure to follow a doctor's directions about taking medicines.
Source: Environmental Protection Agency.