Seven school districts, most in south Sonoma County, announced Thursday they’ll be closed Friday because of poor air quality from the Camp fire in Butte County.

The districts found the air quality index at their campuses registered in the “very unhealthy” range, said Jamie Hansen, spokeswoman for the Sonoma County Office of Education.

The closures include Cinnabar, Dunham, Oak Grove, Old Adobe, Petaluma, Waugh and Wilmar school districts. In addition, the River Montessori Charter School, Live Oak Charter School and the Sonoma County Office of Education’s Headwaters campus, all in Petaluma, will be closed.