Inclement weather has plagued areas of the U.S. in the first half of the weekend, with dangerous conditions including heavy snow, a major ice storm and unsual tornado activity.

Less than two weeks after a tsunami warning, residents were jolted awake before 6 a.m. to consider a new potential disaster scenario.

A storm prompted the first tornado warning in San Francisco on Saturday and caused some damage. Some trees were toppled and roofs were damaged in the city that hasn't seen a tornado since 2005, according to the Weather Service. The damage on the northwest side of the city was being assessed Saturday to determine if there was a tornado.