It will be in effect until fires are out

We've had excessive heat.

We've had high humidity.

Now we have smoke.

Almost a week into an oppressive heat wave, the National Weather Service had added an air quality alert for the region because of all the smoke from brush fires.

The alert is on top of an excessive heat warning that will remain in effect through 9 p.m. Thursday.

The weather service said the air quality alert will remain in effect until the fires are out.

Exposure to particle pollution can cause serious health problems, aggravate lung disease, cause asthma attacks and acute bronchitis, and increase risk of respiratory infections.

The weather service advised residents are advised to use caution as conditions warrant. People with heart or lung diseases should follow their doctor's advice for dealing with episodes of unhealthy air quality.

Additionally, older adults and children should avoid prolonged exposure, strenuous activities or heavy exertion, as conditions dictate.

Much of the smoke has come from the large Lake Fire in northern Los Angeles County that has burned since Aug. 12 and blackened 21,115 acres through Tuesday morning and possibly from the Holser Fire near Lake Piru in Ventura County that has blackened 2,500 acres since it broke out Monday afternoon.

Another fire is burning west of Avenal in Fresno County and still another is burning south of Salinas in Monterey County.