More than 1 million people in the Bay Area were under the brief tornado warning, which was lifted by 6:15 a.m.

Powerful storms swept through parts of Northern California on Saturday, knocking down trees, causing widespread power outages and prompting weather officials to issue what they said was the first-ever tornado warning for San Francisco.

Inclement weather has plagued areas of the U.S. in the first half of the weekend, with dangerous conditions including heavy snow, a major ice storm and unsual tornado activity