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.

A major ice storm has created treacherous driving conditions across Iowa and eastern Nebraska and prompted temporary closures of Interstate 80 after numerous cars and trucks slid off the road.

A powerful storm swept through parts of Northern California early 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.