California declared a state of emergency Wednesday as a powerful storm generated 45-foot waves out at sea, dropped soaking rain on already saturated ground, and prompted warnings of floods and mudslides.

According to the National Weather Service, Wednesday’s storm was predicted to down trees, cause widespread flooding, wash out highways, force slopes to cave in, slow down airports.

At San Francisco Airport more than 70 flights had been canceled as of midday on Wednesday. The area is preparing for a devastating storm that will batter it with powerful winds and copious amounts of rain. The storm-related interruption on Wednesday is less severe than the Southwest Airlines meltdown last week, which resulted in hundreds of flights being canceled, largely in Oakland and San Jose.

49 of the 74 flights canceled at San Francisco International Airport (SFO), where 7% of arrivals and departures were canceled on Wednesday, were operated by the regional airline Skywest Airlines.

On Wednesday, almost 1 in 10 flights nationwide were canceled because to San Francisco.

Before arriving at the airport, travelers travelling out of San Francisco should sign up for their airline’s flight notifications.