When Will the Smoke Clear in the Bay Area? California Fires Cause 'Hazardous' Air Quality

The air quality in several parts of California's Bay Area is expected to remain at unhealthy levels through Wednesday, with a health alert issued through August 26 by Spare The Air, the alert system of the Bay Area Air Quality Management District (BAAQMD).

The air quality is forecast to return to a "moderate" level from Thursday, according to Spare The Air.

A Spare The Air alert is issued "when fine particle pollution is expected to build up to unhealthy levels," the system's website stated.

Smoke from the ongoing wildfires across the state saw the air quality reach "Hazardous (H)" levels on Sunday in parts of the Bay Area's Eastern Zone, including the Rincon Avenue area of Livermore and the Owens Court area of Pleasanton. Both areas recorded an Air Quality Index (AQI) between 303 and 327, the BAAQMD reported.

The AQI represents air pollution concentration levels measured on a scale between zero and 500. "If the concentration of a pollutant rises above 100, air quality can be unhealthy for the public," the Spare The Air website explained.

An AQI at an H level indicates "emergency conditions: everyone avoid outdoor physical activity."

Coastal winds are expected to help disperse some of the smoke in the air, the National Weather Service (NWS) noted Tuesday.

"While smoky and hazy conditions will still be an issue for a lot of locations today [Tuesday], onshore flow from the marine layer will greatly help to clear out some of the smoke near the coast," the NWS said in a post on its official Twitter account.

The air quality in all regions of the Bay Area, including the Northern Zone, Eastern Zone, Coast and Central Bay, South Central Bay and Santa Clara Valley, are expected to be at a "Moderate (M)" level (reporting an AQI between 51 to 100) from Thursday and Friday, according to the air quality forecast published by Spare The Air.

The Eastern Zone and Santa Clara Valley are both expected to retain an "Unhealthy (UH)" level, with an AQI between 101 to 200 forecast for Wednesday.

"Active children and adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else, especially children, should limit prolonged outdoor exertion," when the AQI is at the UH level, the Spare The Air website warned.

The air quality in the Northern Zone, Coast and Central Bay, as well as South Central Bay, is expected to be "unhealthy for sensitive groups (USG)" on Wednesday, with AQIs expected to be between 101 and 150.

When the AQI is at a USG level, "active children and adults, and people with respiratory disease such as asthma, should limit outdoor exertion," the Spare The Air website explained.

More than 600 fires have burned around 1.2 million acres of California following over 13,000 lightning strikes since August 15. Seven people have died, while some 170,000 remain under evacuation orders.