Bay Area air quality remains unhealthy; spare the air alert through Monday

Smoke from the Camp Fire in Butte County, which has cast a pall over the entire Bay Area for more than a week, isn't expected to dissipate significantly until at least Wednesday, according to the Bay Area Air Quality Management District.

Almost the entire Bay Area today has had air quality that, because of the ongoing smoke pollution, is rated as "unhealthy for sensitive groups," which means an "air quality index" count of between 101 and 150.

The exception has been an area that includes Pittsburg, much of Antioch, Concord, Martinez, Pleasant Hill and Walnut Creek in Contra Costa County which, at 4 p.m., had registered in the "unhealthy" range of 151 to 200 AQI.

The U.S. Environmental Protection Agency calculates the air quality index for five major air pollutants -- ground-level ozone, particle pollution (particulate matter), carbon monoxide, sulfur dioxide and nitrogen dioxide.

"For the Bay Area, the main contributor to that count is fine particulates in the smoke," Kristine Roselius, a Bay Area Air Quality Management District spokeswoman, said this afternoon.

The AQI count is expected to rise tonight into Sunday into the 151 to 200 range for almost the entire Bay Area.

"Offshore winds are expected to push the smoke right back over the Bay Area" on Sunday, Roselius said.

WATCH: Meteorologist Rosemary Orozco's Sunday morning air quality report 

Air quality is expected to remain in the "unhealthy" range throughout most of the Bay Area until late Tuesday, before the expected rain arrives Wednesday or Thursday. It will be wind, Roselius said, and not rain that will give the smoke its big bump out of the area.

The entire Bay Area remains under a "Spare the Air" advisory, banning outdoor burning and discouraging driving as much as possible and use of lawnmowers and other engine-driven tools and other machines.