All of California is suffering from the poor air quality. The Bay Area specifically has had 28 consecutive days of bad air. NBC meteorologist Rob Mayeda, showed how bad the air in Yosemite National Park is. It's currently has an air quality index(AQI) of 390, anything over 300AQI is considered hazardous and requires a gas mask.
According to Purple Air, the air quality around Yosemite ranges from 400-600AQI.