The strong winds that are driving the fires are a normal feature of late fall and winter in Southern California. “We haven’t had any meaningful precipitation since March,” Mr. Rolinski said. Helping to spread the fires are the Santa Ana winds, which occur as cold, high-pressure air over Nevada and Utah descend into Southern California, accelerating and warming. Typically, Santa Ana conditions occur on roughly one-third of the days in December and January, Mr. Rolinski said. When the high winds last for just a day or two, Mr. Rolinski said, the region can often get by without a major fire starting and spreading.

Source: New York Times December 06, 2017 14:55 UTC