SONOMA, Calif. — Some of the worst wildfires ever to tear through California have killed 32 people and torched a vast area of the state’s north this week, but the reach of the blazes is spreading dramatically further by the day, as thick plumes of smoke blow through population centers across the Bay Area.

Everything now smells burnt. Hills and buildings are covered in a haze. Residents nowhere near the front lines of the fires now venture out wearing air masks. On a hillside above the Russian River, a broad and menacing band of fire is turning a blue sky into a gray miasma of soot.

Air-quality, based on levels of tiny particles that can flow deep into the lungs, is rated “unhealthy” across much of Northern California, and smoke has traveled as far as Fresno, more than 200 miles to the south. The effects are many: schoolchildren are being kept inside during recess, the Oakland Raiders canceled their outdoor practice on Thursday to prevent players from breathing in the bad air, and doctors are reporting an increase in visits and calls from people with lung and heart trouble.

By Friday morning, the fires that broke out across the state, starting on Sunday, had consumed 221,754 acres, including more than 150,000 acres in Sonoma and Napa Counties, and 34,000 acres in Mendocino County, according to Cal Fire, the state firefighting agency. Fanned by high winds, the fires continued to spread — the largest ranged from 5 percent to 27 percent contained — and had destroyed thousands of homes and businesses.