The Santa Ana is a hot, dry easterly or northeasterly wind and blows from the pass and river valley of Santa Ana, California and thus is named after the valley through which the main flow occurs, and which acts to intensify it as a mountain gap wind. Although the Santa Ana is most common in the Los Angeles area. In Northern California the Los Angeles Santa Ana is also known as Mono and/or Diablo. In the Santa Barbara Area 100 miles northwest of Los Angeles, this wind is known as the Sundowner.
The wind originates over the dry interior plateau, and its temperature and desiccating effects are increased by adiabatic heating during its descent, as with a Foehn wind.
It is the Spring scourge of fruit trees throughout the valley and its peak gusts might reach wind speeds up to 90mph (144kph). Its reach continues across the deserts and through the mountain passes and across the coastal plain. The Santa Ana winds exacerbate an extreme fire danger to all affected areas, especially from August through early December, until the first Pacific winter storms arrive.