What are the Santa Ana winds?

Santa Anas are dry, warm, gusty northeasterly winds that blow toward and offshore from the interior of Southern California, moving in the opposite direction of the normal overland flow that carries moist air from the Pacific into the region.

How are they created?

Santa Anas are formed by high pressure over the Great Basin – the vast desert interior to the west that overlaps several states. The sinking air loses its moisture and flows clockwise toward Southern California, where it must pass high mountain ranges that separate the desert from the coastal metropolitan area. Like a slow-moving river that suddenly narrows and turns into rapids, the air accelerates as it forces its way through mountain passes and gorges, becoming drier and warmer as it descends.

Why do they increase the risk of forest fires?

With a Santa Ana wind, humidity often drops to single digits. The extreme lack of humidity causes vegetation – living and dead – to dry out severely and become vulnerable to fires.

The enormous wind speeds can fan any spark – from a downed power line to a cigarette bud – into a rapidly spreading wildfire.

Santa Anas is associated with some of Southern California’s worst wildfires, including the Woolsey fire, which killed three people and destroyed more than 1,600 structures in November 2018, and the Franklin fire, which killed nearly 50 homes in the Malibu area damaged or destroyed.

How did they get their name?

A generally accepted explanation is that the name is associated with Santa Ana Canyon in Orange County. Other theories persist, along with other nicknames including “Devil Winds.”