As wildfires continue to blaze in around Sonoma and Napa counties in northern California, weather conditions have carried the smoke well beyond the immediately affected areas.

Air quality in areas as far away as San Francisco and San Mateo County—more than 80 miles from the heart of the fires—is reaching historically poor levels. According to the San Francisco Chronicle the thick smoke “resulted in the worst air quality ever recorded near the heart of the North Bay fires.”

Read: Sonoma and Napa Wineries Damaged by California Wildfires: Updated List

Several counties in the Bay Area have issued hazardous level warnings as the poor air quality is expected to persist. The Environmental Protection Agency index increased the San Francisco area’s level to orange, which signifies that sensitive groups such a children, the elderly, and those suffering from respiratory conditions should avoid going outside and exerting themselves where possible. Some residents are already reporting respiratory issues and becoming ill from the smoke, and many are donning protective masks.

Schools across the region have already issued warnings to limit outdoor activity, with many bringing recess and P.E. classes indoors. Sonoma and Napa schools remain closed indefinitely, with other school districts evacuated or issuing closures for the rest of the week. The smoke health advisory is currently extended through Sunday—a week after the fires began.

Read: California Wildfires: See Photos of the Inferno Destroying Wine Country

The fires are now estimated to have destroyed more than 2,000 homes and businesses across eight counties. More than 15 people are reported dead and 200 missing.