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Seawater floods highways and low-lying communities near California beaches. The cause: so-called "king tides" pulling the Pacific Ocean farther ashore than normal.

WHAT IS A KING TIDE? King tide is a layman's term used to describe one of the highest tides of the year. Besides producing higher-than-normal tides, experts say such an event — scientifically known as perigean spring tide — also results in some of the lowest tides.

WHAT CAUSES THEM? King tides are natural phenomena. They occur when the Earth, moon and sun align and cause increased gravitational pull on the Earth's oceans. HOW OFTEN DO THEY OCCUR? King tides occur several times a year, repeating over several days, and can be predicted ahead of time.

If a coastal storm hits during a king tide event, "the effects would be worse. You would have more coastal flooding in low-lying areas," said Stephen Gill, a senior scientist at the National Oceanic and Atmospheric Administration.

WHAT IS THE ORIGIN OF THE NAME? It's believed to have been coined in Australia and the South Pacific by locals to refer to an especially high tide. Its usage has crept into the United States and Canada.

WHY THE FUSS? In addition to the nuisance and potential damage, coastal residents in recent years have been encouraged to take photographs during king tides and share them on social media sites like Flickr. Environmentalists say this may help people visualize what rising sea levels might look like if predictions about the Earth's climate come to pass.