The San Joaquin Valley Air Pollution Control District has issued an air quality alert for the entire region through Thursday, October 7.
A high-pressure system has trapped the smoke within the Valley region. ABC30 Meteorologist Madeline Evans says the air quality was unhealthy for all Central California counties on Monday.
Air officials say they don't expect the haze to clear until a low pressure system moves in toward the end of the week, pushing out the smoke.
The air district warned residents to remain indoors as much as possible to reduce their exposure to particulate matter emitted from the smoke.
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Before heading outdoors, you can check air conditions online.