At least five wildfires are ravaging Southern California, and the three largest have already killed at least five people, burned tens of thousands of acres and prompted the evacuation of an estimated 179,

The winds are common in California in the colder months, but they can sometimes help spread dangerous wildfires.

Santa Ana winds are caused by strong high pressure over the Great Basin region of the West creating a pressure gradient that amps up winds through the mountains, foothills and sometimes valleys of Southern California. In this case, the winds are getting a major boost from a strong upper-level low pushing southward across the state.