A wildfire burning out of control in rural Northern California sent a stream of smoke over 70 miles south into the San Francisco Bay Area over the weekend. The County Fire in Yolo and Lake Counties has burned at least 50 square miles northwest of San Francisco, and is only 2 percent contained, according to the California Department of Forestry and Fire Protection. No injuries have been reported so far, but the blaze fueled by hot air and dry winds threatens more than 100 structures. Smoke from the fire drifted south, contributing to poor air quality across the Bay Area The agency said there was a “yellow” air quality alert due to the fires. “People with heart/lung disease, older adults, and children should consider reducing prolonged/heavy exertion,” the agency said.