There’s no other way to describe it — the air in San Francisco is atrocious. Ash and soot from wildfires in wine country fell across the Bay Area on Monday. Health officials are telling people who are particularly sensitive to pollution that maybe they should leave town for a while.

And “a while,” is at least through the weekend.

Daniel Alrick, a meteorologist for the Bay Area Air Quality Management District, said winds flowing from the ocean to the land improved conditions overnight, but that’s about to change again on Wednesday.

“We expect conditions to deteriorate considerably [on Wednesday] as winds shift to northerly behind a dry cold front,” which will push smoke south into the Bay Area.

It’s not just San Francisco. Smoke from what is being called the Canyon 2 fire, burning in the Anaheim Hills, was pushed west Monday, making Disneyland look more ominous than adventurous.

In San Francisco, summer and fall weather tends to be extraordinarily predictable. In the morning, skies tend to be clear over the Bay Area before things start heating up. By the afternoon, the winds start blowing from the cool ocean to the hot land in North and East Bay. It’s a sea breeze with a cool, foggy marine layer that, in better circumstances, would provide some natural aid to crews battling the fires.

Unfortunately, any daily relief will be fleeting to nonexistent. The sea breeze will be weak, and that cool, damp marine layer? Nope — not beyond the coastal areas. For basically all of the Bay Area, winds will be out of the north most of the time through at least the weekend.

This is bad news for people who enjoy breathing clean air. Even if the fires can be reined in, parts of North Bay will still be burning and producing giant plumes of air-polluting smoke. With winds from the north through the weekend, the choking conditions can be expected to continue.

Wildfire smoke over California seen from satellite Oct. 10, 2017. (NASA)

“It literally smelled like a campfire Monday and Tuesday,” Alrick said of his Haight Ashbury home, “despite the actual fires being more than 40 miles away.”

The Air District activated a health advisory on Tuesday, warning people of “unprecedented levels of air pollution throughout the Bay Area.” Current PM2.5 levels — the particles that are especially dangerous to human health — are at the highest levels recorded since air-quality measurements began in 2009.

PM2.5 are particles in the air that are about 3 percent of the diameter of a human hair. The size is what makes them so dangerous. Because they’re so small, they can enter the lungs and even the blood stream.

Air-quality forecasters are telling people to stay in buildings with filtered air. They even go so far as to recommend that sensitive populations leave the region entirely for less-affected places until the smoke subsides.