Heat, smoke back to choke the region

Spare the Air Alert extended through Friday as quality of skies deteriorates

Many Bay Area residents woke up to a double whammy Monday morning: scorching temperatures and smoky air. Again.

Air quality in the Bay Area began to deteriorate early Monday morning, as smoke from several Northern California wildfires — including the new, outofcontrol Glass Fire in St. Helena — pushed into the region. Airquality regulators announced a Spare the Air Alert would run

through at least Friday.

The combination of wildfire smoke and high temperatures will likely choke a region already wearied by weeks of poor air quality this month. Officials urged people to stay inside.

Air quality in the eastern portion of San Francisco was considered unhealthy for sensitive groups by the early afternoon, while other areas remained better off, according to data from airquality tracking website PurpleAir. The air was worse in parts of the East and South bays. And the site warned of “serious health effects” from the air in Santa Rosa, Rohnert Park and surrounding areas.

The Glass Fire in St. Helena, which ignited just before 4 a.m. Sunday, was responsible for much of the smoke, according to the Bay Area Air Quality Management District. Wind gusts reached 60 mph on Mount St. Helena on Sunday evening, with the winds blowing toward the southwest.

The air was considered hazardous in parts of the North Bay, where multiple wildfires were burning. The sky turned a deep red in Santa Rosa, as several blazes — the Glass, Shady and Boysen fires — merged into one, threatening 8,500 structures across Napa and Sonoma counties. Ash fell from the sky.

Dangerous fire conditions are expected to continue through Monday evening. The combination of the winds and heat are expected to exacerbate existing fires, and make it easier for new ones to ignite.

The regional air district extended a Spare the Air Alert it had issued Sunday through Friday and urged residents in areas affected by wildfire smoke to stay indoors. The entire Bay Area recorded unhealthy levels of smog and particle pollutants as of Monday afternoon.

A red flag warning has been issued for much of Northern California, stretching from the Oregon border down to San Jose and east to the Sierra foothills. The warning encompasses the August and North complex fires, hampering efforts to contain those behemoths.

The entire Bay Area recorded unhealthy levels of smog and particle pollutants as of Monday afternoon.

Photos by Brittany Hosea-Small / Special to The Chronicle Smoke hangs above the horizon as the sun peeks from behind it during the Glass Fire near Calistoga.

Smoke from the Glass Fire rises above the trees along Calistoga Drive in Calistoga. Winds have carried the smoke across the Bay Area again.

Nick Otto / Special to The Chronicle Smoke from wildfires earlier this month obscures the Bay Bridge and San Francisco skyline. New fires in Wine Country have sent smoke into the region again.