Since the first flames sparked in the Santa Ana winds on January 7, at least 16 have been confirmed dead, 12,000 structures have been destroyed, and over 150,000 residents have been ordered to leave their homes.

Santa Ana winds occur when air flows west from a region of high pressure over the dry Great Basin to lower pressure off the California coast, According to Accuweather. As that cool interior air flows over and through mountain passes, it accelerates, sinks and compresses.

By the time the winds get to the point where the Eaton Fire broke out in Altadena on Jan. 7, it’s not uncommon for them to have less than 5 percent relative humidity, meaning essentially no moisture at all.

Santa Ana winds in Southern California are often-fierce winds that topple power lines and trees and can turn a spark into a raging wildfire.

The Palisades, Eaton, and Hurst fires covered more than 5,600 acres of Southern California as of Wednesday morning. Tens of thousands were under mandatory evacuation orders but the fires increased in size overnight, helped by the blustery Santa Ana winds.

The Eaton Fire – one of a multitude of wildfires incinerating the Los Angeles area – is still burning with little containment on Saturday as the Santa Ana wind event fueling the blazes is set to continue into next week.