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.

San Francisco residents were woken up by a tornado warning early Saturday morning during a powerful storm system that battered the region with heavy rain and wind.

For the first time in recorded history, downtown San Francisco was issued a tornado warning on Saturday as severe storm conditions swept through the city, prompting local authorities to warn residents of the rare threat.