"Santa Ana winds are extremely dry downslope winds that originate inland over the dry deserts of Southern California," AccuWeather explains. "The northeasterly winds encounter the Transverse Ranges that separate coastal Southern California from the deserts."
When these winds travel through passes and canyons, their speed increases. As they descend, they become even drier as the air is heated.
"The end result is strong and very dry winds infamous for fanning regional wildfires," according to AccuWeather.