A potent winter storm targeting Northern California this weekend brought what appears to be the first official tornado warning on record for the city of San Francisco on Saturday morning.

San Francisco experienced its first-ever tornado warning early Saturday, stunning residents as a powerful storm swept through the Bay Area, bringing heavy rain and winds. The warning prompted a flood of social media posts from residents startled awake by emergency alerts.

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.