From the looks of things Thursday, the Bay Area’s air quality is getting worse.

In San Francisco, the air quality index rose to 245 late Thursday afternoon, according to the Bay Area Air Quality Management District. For the past week since the wildfires began, the air quality had remained between 150 and 200, a level considered “unhealthy” by the EPA. Once the index rises above 200, the air is considered “very unhealthy.”

Other cities in the Bay Area also saw the air quality readings reach very unhealthy levels. San Pablo, a city 19 miles northeast of San Francisco, had a reading of 263 Thursday afternoon. Oakland showed a reading of 248 while Berkeley’s reading was 247. UC Berkeley’s chancellor notified the university’s 42,000 students that all classes would be canceled Thursday afternoon as well as Friday.

Residents in Chico, 150 miles northeast of San Francisco and close to the Camp Fire, had it worse. Air quality readings have reached above 300 this week, which the EPA terms “hazardous.” Yuba City, 45 miles south of Chico, had a reading of 455 Thursday morning, while Muir Beach, a coastal town in Marin County, also had a reading above 357, according to IQAir.

The smoke is being carried by winds from the Camp Fire in Butte County, now the deadliest and most destructive fire in California history. The wildfire has injured at least three firefighters and burned more than 10,000 structures since it began on Thursday, Nov. 8. At least 56 deaths have been reported and 130 people are still unaccounted for.

Residents and businesses have been spending most of the past week staying indoors. Air purifiers and respirator masks have sold out of many stores, and the best selling product in Amazon’s “tools and home improvement” category is a 10-pack box of 3M respirators. Health officials and volunteers in the Bay Area have been handing out face masks to homeless people, who may not have anywhere indoors to keep away from the smoke.