The heat wave baking Southern California not only raises the risk of wildfires and heat-related illness but could bring another hardship: bad air quality.
The South Coast Air Quality Management District issued an air quality alert for inland areas of the South Coast Air Basin and the Coachella Valley because of elevated levels of ozone, likely causing poor air quality during the afternoon and early evening. The alert went into effect Friday at 2 p.m. until Tuesday at 8 p.m.
High temperatures often lead to more pollutants in the air — specifically ozone, the main pollutant during the summertime.
The AQMD has forecast good-to-moderate air quality for coastal regions and Orange County for Tuesday. Central and Southeast portions of Los Angeles County and Antelope Valley are projected to have moderate air quality, with ozone being the primary pollutant.
But the air quality is expected to be unhealthy for sensitive groups in Western and eastern San Gabriel Valley, Pomona, Walnut Valley, Santa Clarita Valley and the San Gabriel Mountains. That means that pregnant women, children, older adults and people with heart or lung disease should avoid heavy outdoor exertion.
"It's the high temperatures that increase the contents of ozone in the air and we also have very weak winds, which allows the air to stagnate," said National Weather Service meteorologist David Sweet. "All that ozone production occurs over the city and just sits there."
Ozone air pollution can lead to problems with respiratory health, including asthma attacks, trouble breathing and lung damage. Older adults, children and people with chronic obstructive pulmonary disease or asthma could be more sensitive.
Air quality can fluctuate depending on weather and time of day. To mitigate pollution levels, people should should try to limit the usage of gasoline-powered garden and lawn equipment until the evening, set their air conditioners to a higher temperature, conserve electricity and try to delay the use of household chemicals and trips to the gas station until the evening.
Southern California has been grappling with triple-digit high temperatures over the last week during a "heat dome" that trapped heat near Earth's surface and kept the region warm.
Tuesday is forecast to be the coolest day of the week due to weaker high pressure and strong onshore winds, according to the weather service. Temperatures are expected to drop by 2 to 4 degrees in most areas, while it could be cooler than normal near coastal regions and hotter than normal inland.
"We're cooling down just a little bit," Sweet said. "It's going to go back up this weekend but we're not sure it's going to be quite as warm as last weekend."
It's expected to warm back up Friday into Saturday, bringing temperatures just below heat warning levels. Interior regions could end up seeing heat advisories and warnings if temperatures climb high enough. Saturday is expected to be the warmest day, with high temperatures forecast to be 8 to 12 degrees above normal in the warmest areas.
Overnight high temperature records were broken Monday night into Tuesday morning for Lancaster and Palmdale, where it reached 86 and 84 degrees respectively. The previous record was 82 and 79 degrees.
Downtown Los Angeles is forecast to see temperatures in the upper 70s to the 80s through Wednesday before climbing back into the mid 80s and 90 by Friday.
Antelope Valley will likely be the warmest area in the region, with projected highs between 96 and 104 through Wednesday and 99 and 108 degrees over the weekend.
About 38.5 million Californians live in communities with unhealthy levels of fine particles or smog, according to the American Lung Assn.'s annual "State of the Air" report, which has served as a national scorecard for the two major air pollutants since 2000.
