A tornado warning has been issued for the first time ever in San Francisco, as thunderstorms swept through the region, toppling trees and causing major power cuts.
The advisory was issued just before 06:00 local time (14:00 GMT) on Saturday for northern San Mateo County and parts of downtown San Francisco.
The storm caused power outages for more than 221,000 people across Northern and Central California, according to the PowerOutage website.
The city last saw a tornado in 2005, though that struck without any clear radar signature, so no warning was issued in that case, National Weather Service (NWS) meteorologist Roger Glass told AP news agency.
More than one million residents were woken on Saturday morning in San Francisco and its suburbs to alerts on their mobile phones, warning them to “take shelter now”.
Winds of up to 60mph (96km/h) ripped through the area, the NWS said.
But a few minutes later, NWS Bay Area said the warning was over and the storm had moved out of the city’s downtown.
Authorities were assessing the damage to determine if a twister had occurred.
Nearby San Mateo County was last issued a tornado warning in 2011.
NWS Bay Area warned that residents should still steer clear of the seaside over the weekend, with a coastal flood advisory in place until Monday.
San Francisco’s tornado alert came just a week after the city saw its first ever tsunami warning
The brief advisory was issued for northern California and southern Oregon following a magnitude 7.0 earthquake that hit off the northern coast of the state.
It was later rescinded, and no injuries were reported.
