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.

For the first time in recorded history, downtown San Francisco was included in a tornado warning on Saturday as severe storms swept through the city, just one week after a tsunami warning triggered widespread panic in the region.

A strong atmospheric river drenched northern California with heavy rains and damaging wind gusts Saturday, leaving well over 200,000 without power in the state.